Item Generation Tutorial

This massive article explains item generation in great detail; far more detail than casual gamers are likely to be interested in. Skim this item generation encyclopedia by the chapter headings if you want one specific question answered. Read it cover to cover if you really want to understand how the game works.

For a similar article discussing item generation in earlier versions of the game, check out the v1.09 Item Generation Tutorial.

Basics

The goal of most players in Diablo II is to kill enemies while staying alive. There are three things that largely determine how effective your character is at this goal:

1. Your tactics.
2. The build of your character.
3. The items used by your character.

All three have a great impact on gameplay -- characters die quickly on Hell difficulty if they play without wise tactics and kill slowly with poor skill distribution, but most players find that the essential element is proper use of items. A magic using character will see her effectiveness increase dramatically if she doubles her skill levels, and the effectiveness of a melee fighter or bow user is a direct reflection of the quality of their weapon. As a result, most players spend hours seeking top quality items, and then hours more trying to improve their gear further. At the highest end, most truly dedicated players spend virtually all their game time item hunting.

This guide explains how best to find the items you seek, and explains why this task often seems so difficult.

Terminology

• Item Type: The kind of item; a cap, a gem, a short sword, a ring, etc.
• Item Quality: Different qualities of the same item type. These are, in order of increasing scarcity: low quality > normal > superior > magic > rare > set > unique.
• Affixes The magical modifiers on an item; prefixes and suffixes. (Not all item properties are affixes. For example: stuffmods, pre—defined properties of crafted items and some special mods of set and unique items. E.g. "+60 to Mana" on magic ring is affix, "+20% crushing blow" isn't affix.
• Qlvl: Quality level. 1) A level of item type. All these levels are stored in the weapons.txt, armor.txt and misc.txt data files. 2) A level of set or unique item. All this levels are stored in UniqueItems.txt and SetItems.txt data files.
• Ilvl: Item Level. All items in the game have levels. These levels are generated when the item is created. This value is not displayed in the game, so identical items can have very different ilvls, depending on which monster dropped them. Be sure not to confuse Item Level with the item's level requirement -- they are different things.
• Mlvl: Monster Level. All monsters in the game have levels as well as players. These are determined largely by the level upon which a monster spawns. (The same monster type found on different levels will have different mlvls.)
• Area Level: Area Level. All areas in the game also have levels. These determine or at least factor into mlvl, ilvl, and more.
• Alvl: Affix Level. It is a level of prefix or suffix. They are stored in MagicPrefix.txt and MagicSuffix.txt in "Level" column. The name "Affix Level" is used to differ them from other "Levels".
• TC: Treasure Class. All item types in the game are organized into treasure classes. In v1.10 there are 29 weapon and 29 armor Treasure Classes (see those here), with additional TCs covering all the smaller, miscellaneous items such as runes, charms, gems, potions, etc. All TCs are recursive: this means that one treasure class may include another treasure class. E.c. Hell Baal drop all his items from "Baal (H)" treasure class, which consists of "Act 5 (H) Equip B", "Act 5 (H) Junk" and "Act 5 (H) Good" treasure classes. Each of them consists of several other treasure classes, each containing fewer entries and growing more specific.
• Clvl: Character Level. It is one of few levels, that you can actually see in the game.
• Rarity:Rarity is a value assigned to every set and unique item in the game. This comes into play largely when there are more than one unique or set item of the same type, and makes some such items much more common than others. For example, the unique ring Stone of Jordan has a Rarity of 1, while the far more common unique ring Manald Heal has a Rarity of 15.
• SP:Single Player mode.

Short Explanation of Drop Process

When you kill a monster or open a chest the game may generate items to reward you. The properties of these items are generated at that moment, even though the item may be unidentified. The game creates dropped items with algorithm of such kind:

1. At the beginning it finds treasure class (TC), that describes all drops of the monster you killed, a chest you opened, a hidden stash you found, etc. All drop sources have treasure classes.
2. The game then makes one or several iterations, that are called "Picks", when it selects one choice from several possibilities.
   1. One of the possibilities is "NoDrop", which does what it sounds like. Many monsters have multiple "picks," so even if one of them is NoDrop, the other picks may overrule it. Most normal monsters have only one pick, though.
   2. If nothing is selected from the first TC, the next one down the list will be consulted, then the next, then the next, until an item or NoDrop is selected.
3. Once an item is selected, the item properties are determined. Since most items have numerous possible types, game's algorithm of quality determination is highly complicated. Items such as keys, runes, and potions are only found in normal quality, but items like rings, short swords, helms, and bucklers have different qualities like magic or unique. Note that Magic Find is checked during this step.
4. For every selected item an ilvl is calculated.
5. If the rarity check hits upon an item of unique or set quality, the game creates the list of all valid item types (determined by their ilvl) and randomly selects one to drop. If there is not a unique of that type, a rare item with triple durability will generate. If there is no set item of the selected type, a magical item with double durability will appear.
6. After the game selects item type and item quality, it generates item affixes if needed. It also generates all other properties of an item, if there are such properties. Items like Runes, mana potions, and identify scrolls doesn't have variable properties, but magic rings, rare kite shields, cracked sashes needs property generation.

A simplified example in action: Mephisto is killed! What does the game do to determine your reward?

1. calculates the number of items to drop
2. selects item types
3. selects item qualities
4. selects certain unique or set items if needed
5. selects item properties

Game Data Files

This section discusses the data files that are used in item generation process.

Many parameters of drops are stored in txt files, that are packed to MPQ files when Diablo II is installed. If you have installed ATMA you may find that files unpacked in its data folder. These files are stored in CSV format, a plain text format that may be viewed with Excel or OpenOffice.org. You do not need to know everything about these complicated files to be effective in item hunting, but it will help if you know something about their structure. Truly dedicated item hunters will want to dig deeper into the files, and will find the D2 file guides posted at the Phrozen Keep, of value.

TreasureClassEx.txt

This is the most important file. It organizes all droppable items into a system of Treasure Classes. Since each source of items in the game (except NPCs) drop items from Treasure Classes, this is crucial to understand.

We'll start with description of all fields of TreasureClassEx.txt table.

• Treasure Class: The name of a TC, one the game usually refers to.
• Group: An identification number of similar TCs. This is used in TC upgrade process according to Mlvl.
• Level: The level of a given TC. It is also used in TC upgrade process.
• Picks: A quantity of iterations of the selection process.
  • Unique: A modification number for chance to drop unique item from given TC (more is better).
  • Set: A modification number for set chance.
  • Rare: A modification number for rare chance.
  • Magic: A modification number for magic chance.
• NoDrop: A rate of skipping drops from the TC (the higher NoDrop, the less items the TC will generate).
• Item1-Item10: A code of item to drop or a name of TC to drop from (item codes are stored in weapons.txt, armor.txt and misc.txt data files).
• Prob1-Prob10: A rate of selecting respective Item1-Item10 (more is better).
• SumItems, TotalProb, DropChance, Term Unimportant fields for item drop routine.

TreasureClassEx.txt file doesn't contains all treasure classes. At run time the game adds quite a few additional TCs. Their names are ArmoXX and WeapXX, where XX is two digit number. The game creates them from the armor.txt and weapons.txt files, by looking at quality levels. The first TC of armors, Armo03, contains all armor items with levels from 1 to 3: Cap, Quilted Armor, Leather Armor, Buckler, Gloves, Boots and Sash. The next armor TC, Armo06 contains all armor items with levels from 4 to 6, and so on. The last armor TC, Armo87, contains all armor items with levels from 85 to 87. Weapons are organized in their TCs, Weap03-Weap87 by the same manner.

In this TCs Prob1-Prob10 values determine how likely the given items in those TCs are to drop. Some items have penalties and are therefore seen less frequently. A few of these, for illustrative purposes:

• Normal items: 3
• Assassin claws: 2
• All other class-specific items: 1
• Wands/Staves/Scepters: 1

These values interact with how many items are found in a given TC to create item shortages and abundances. The given items in a TC with 12 items will be comparatively less common than the items in a TC with 7 items. And if those 7 items include several wands and claws, the normal items in that TC will be highly overrepresented. Breast Plates, for instance.

To further demonstrate, let's look at the process of item selection from a given TC.

All monsters have treasure classes, written in monstats.txt file. When you kill a monster in normal difficulty the game simply uses its TC to drop items. However in Nightmare and Hell difficulty the given TC may be upgraded. When determining the TC for a monster, the game selects the highest level TC in the group that is equal to or less than the Mlvl. If there is no group for TC of this monster, than it doesn't upgrade TC. Treasure classes that are included in the selected TC aren't upgraded.

Selecting from a TC the game makes one or several attempts of dropping according to Picks field. Each pick choses from several possibilities, including NoDrop, and each non-empty entry from Item1-Item10 fields. The chance of every choice is equal to X/Sum, where X is respective value from Prob1-Prob10 fields for Item1-Item10, or NoDrop value for NoDrop choice, and Sum is the sum of all that values (NoDrop+Prob1+Prob2+...+Prob10).

If the game selects another TC during this process it will initiates the same cycle for it, then another cycle for newly selected TC, then another and another until it selects an item or NoDrop.

In multilayer game NoDrop value is reduced.

NewNoDrop=int( ProbSum/(1/((NoDrop/(NoDrop+ProbSum))^N)-1) ), where N=int (1+AdditionalPlayers/2+ClosePartiedPlayers/2), AdditionalPlayers — the number of all additional players in the game, where the monster is killed, ClosePartiedPlayers — the number of players in your party near you (not far than two screens away), ProbSum=Prob1+Prob2+Prob3+...+Prob10, int — operation of truncating fractional part of a number.

In SP the Players X command sets the number of NON-partied players, e.g. /players8 command sets N=4.

For example: a character kills a non-boss Devilkin in The Pit level 1 in Hell in /players8 mode (or in a full game on Battle.net). The Devilkin has Mlvl=85. In monstats.txt file Devilkin is figured under "fallen3" name. Non-unique fallen3 drop items from "Act 1 (H) H2H B" TC in Hell difficulty. In TreasureClassEx.txt file "Act 1 (H) H2H B" TC has group=7 and level=66. Because Mlvl=85 the TC is upgraded to "Act 5 (H) H2H C" TC, which has level=85 (less or equal to mlvl). So Devilkins in The Pit drop items from "Act 5 (H) H2H C" TC.

It has 1 pick from fallowing possibilities:

• NoDrop (100);
• gld (21);
• Act 5 (H) Equip C (16);
• Act 1 (H) Junk (21);
• Act 5 (H) Good (2).

The numbers in (parenthesis) are probabilities.

Lets calculate NewNoDrop:

• ProbSum=21+16+21+2=60.
• NoDrop=100.
• N=4.
• NewNoDrop=int( 60/(1/((100/(100+60))^4)-1) )=11.

So The Pit Devilkin has fallowing chances:

• 11/71 for dropping nothing
• 21/71 for dropping gold
• 16/71 for dropping from Act 5 (H) Equip C
• 21/71 for dropping from Act 1 (H) Junk
• 2/71 for dropping from Act 5 (H) Good

Lets assume, that the game decided to drop from "Act 5 (H) Equip C" TC. Here it is: Picks=1, NoDrop=0, Item1="weap81", Prob1=2, Item2="armo81", Prob2=1, Item3="weap84", Prob3=6, Item4="armo84", Prob4=3, Item5="weap87", Prob5=14, Item6="armo87", Prob6=7, Item7="weap87", Prob7=1, Item8="armo87", Prob8=1, Item9="Act 5 (H) Equip B", Prob9=1530. Note, that weap87 and armo87 TCs are mentioned twice, it is not a error.

So this TC has fallowing chances:

• 2/1565 for dropping from weap81;
• 1/1565 for dropping from armo81;
• 6/1565 for dropping from weap84;
• 3/1565 for dropping from armo84;
• 15/1565 for dropping from weap87;
• 8/1565 for dropping from armo87;
• 1530/1565 for dropping from "Act 5 (H) Equip B".

Lets assume, that the game decided to drop from armo87. This TC has picks=1, NoDrop=0, Item1="Diadem", Prob1=3, Item2="Corona", Prob2=3, Item3="Sacred Armor", Prob3=3, Item4="Ogre Gauntlets", Prob4=3, Item5="Myrmidon Greaves", Prob5=3, Item6="Colossus Girdle", Prob6=3, Item7="Dream Spirit", Prob7=1, Item8="Guardian Crown", Prob8=1, Item9="Vortex Shield", Prob9=1, Item10="Bloodlord Skull", Prob10=1.

So armo87 has fallowing chances:

• 3/22 for Diadem;
• 3/22 for Corona;
• 3/22 for Sacred Armor;
• 3/22 for Ogre Gauntlets;
• 3/22 for Myrmidon Greaves;
• 3/22 for Colossus Girdle;
• 1/22 for Dream Spirit;
• 1/22 for Guardian Crown;
• 1/22 for Vortex Shield;
• 1/22 for Bloodlord Skull.

Monstats.txt

This file holds a lot of information about monsters. The fields in this file are as follows:

• Id: Internal name of a monster type, the game refer to a monster using this field.
• NameStr: OIt is either the actual name of the monster or a reference to name table for names with spaces.
• rangedtype: 1 for monsters with ranged attack, blank for others.
• minion1 and minion2: Type of minions for the monster, e.g. normal fallen shamans usually have normal fallens as minions.
• PartyMin-PartyMax: The range for quantity of minions.
• MinGrp-MaxGrp: The range for quantity of normal monsters in one grope.
• Velocity: Movement speed, walking, flying, etc.
• Run: Run speed. Only a few monsters can run at a different speed than they walk.
• Level: Monster level in Normal difficulty.
• Level (N): Only for bosses. Monster level in Nightmare difficulty
• Level (H): Only for bosses. Monster level in Hell difficulty.
• lUndead: 1 for melee undeads.
• hUndead: 1 for ranged undeads.
• demon: 1 for demons.
• boss: 1 for bosses. They save their mlvl in Nightmare and Hell difficulties.
• Drain, Drain(N), Drain(H):Life and mana leech effectiveness in Normal, Nightmare and Hell difficulties (percents).
• coldeffect, coldeffect(N), coldeffect(H): Chill and freeze effectiveness in Normal, Nightmare and Hell difficulties (listed in percentages).
• ResDm, ResDm(N), ResDm(H): Damage resistance in Normal, Nightmare and Hell difficulties (percents).
• ResMa, ResMa(N), ResMa(H): Magic resistance.
• ResFi, ResFi(N), ResFi(H): Fire resistance.
• ResLi, ResLi(N), ResLi(H): Lightning resistance.
• ResCo, ResCo(N), ResCo(H): Cold resistance.
• ResPo, ResPo(N), ResPo(H): Poison resistance.
• ToBlock, ToBlock(N), ToBlock(H): Chance to block.
• Crit: Critical hit chance (5% for every monsters as of now).
• TreasureClass1: TC of normal monster in Normal difficulty.
• TreasureClass2: TC of champion monster in Normal difficulty.
• TreasureClass3: TC of unique monster in Normal difficulty (non-quest drop).
• TreasureClass4: TC of unique monster in Normal difficulty (quest drop).
• TreasureClass1(N): TC of normal monster in Nightmare difficulty.
• TreasureClass2(N): TC of champion monster in Nightmare difficulty.
• TreasureClass3(N): TC of unique monster in Nightmare difficulty (non-quest drop).
• TreasureClass4(N): TC of unique monster in Nightmare difficulty (quest drop).
• TreasureClass1(H): TC of normal monster in Hell difficulty.
• TreasureClass2(H): TC of champion monster in Hell difficulty.
• TreasureClass3(H): TC of unique monster in Hell difficulty (non-quest drop).
• TreasureClass4(H): TC of unique monster in Hell difficulty (quest drop).
• TCQuestId and TCQuestCP: Values for special quest drops like Mephisto's Soulstone.

The most important part for item drops is Treasure Classes of the monster and his level.

Magicprefix.txt and Magicsuffix.txt

These two files contains all affixes available in the game. They have almost the same field, so they're covered in the same section in this guide.

• Name: The name of the affix as it appears in the game.
• version: 0 for Classic, 100 for LoD.
• spawnable: 1 for available affixes, 0 for affixes, that cannot appear in the game.
• rare: 1 for affixes, that can appear on rare items, 0 for magic only affixes.
• level: Minimum Affix Level of an item that may spawn with this affix.
• maxlevel:Maximum Affix Level of an itemthat may spawn with this affix.
• levelreq: Minimum required character level for using item with this affix.
• classspecific: The class for which this affix will work, — ama, sor, nec, pal, bar, dru. (ArchAngel's prefix will only add skills for sorceress, for instance.)
• classlevelreq: Minimum required character level for using item with this affix. Although it usually is overrules by levelreq.
• frequency: The rate of appearance in the game of this affix (0 for items that cannot be selected at all).
• group: Group Id for selecting affixes for rare and crafted items. They cannot have more than one affix per group.
• mod1code, mod2code, mod3code: The codes of effects of this affix. This codes refer to internal game functions, however all of them are quite self-explanation, e.c. "ac%" is Armor Class increase, "dmg%" is Damage increase, "res-all" is resist all.
• mod1param, mod2param, mod3param: Parameters for the affix function. E.c. poison duration in frames, skill index, cold duration in frames. (Diablo II runs at an internal clock speed of 25 frames per second.)
• mod1min, mod2min, mod3min: Minimum parameters for affix function such as minimum of life range given by +life affix
• mod1max, mod2max, mod3max: Maximum parameters for affix function such as maximum of life range given by +life affix.
• transform: 1 for affixes that do palette shift on base item.
• transformcolor: Color code for affixes that do color shift on base item; "dgld" is dark gold, "lpur" is light purple, edtc.
• itype1, itype2, itype3, itype4, itype5, itype6, itype7: Include Type, item type codes of items, on which this affix may occur. These codes are stored in armor.txt, weapon.txt, misc.txt and ItemTypes.txt files.
• etype1, etype2, etype3, etype4, etype5, etype6, etype7: Exclude Type, item type codes of items, on which this affix may NOT occur.
• divide, multiply, add:Values for modifying item price.

The usage of these files is explained in more detail in chapter 11, when affix generation is covered.

Weapons.txt

This file is used to store information about weapon item types.

• name: The name of the weapon as it appears in the game.
• type, type2: Item type code, the index of respective raw in itemtypes.txt file.
• code: Internal item name.
• alternateGfx: Item code for choosing animation. Unimportant for item generation.
• namestr: Reference to the table. Contained correct name of the item.
• version: 0 for Classic, 100 for Lod.
• compactsave:Empty. Unimportant for item generation.
• rarity: The rate of dropping the weapon from weapon racks.
• spawnable:0 for items, that cannot be generated (except special cases like quests), 1 for others.
• mindam-maxdam: One-handed damage.
• 1or2handed: 1 for two-handed weapons that may be held in one hand by the Barbarian.
• 2handed: 1 for two-handed weapons.
• 2handmindam-2handmaxdam: Two-handed damage.
• minmisdam-maxmisdam: Ranged damage.
• rangeadder: Weapon range adder. Weapon range=1+rangeadder.
• speed: Base weapon attack speed.
• StrBonus: Strange bonus for weapon damage. Enhanced damage percent=Strength*StrBonus/100.
• DexBonus: Dexterity bonus for weapon damage. Enhanced damage percent=Dexterity*DexBonus/100.
• reqstr: Strength required.
• reqdex: Dexterity required.
• durability: Base durability.
• nodurability: 1 for indestructible weapons.
• level: Quality Level.
• levelreq: Character level required.
• cost: base weapon cost.
• gamble cost: gambling cost.
• magic lvl: Magic Level (see chapter 11 and chapter 22).
• auto prefix: The code number of prefix, that always occurs on the weapon (like +mana on orbs).
• OpenBetaGfx: Unimportant for item generation.
• normcode: Code of normal version of the weapon.
• ubercode: Code of exceptional version of the weapon.
• ultracode: Code of elite version of the weapon.
• wclass, 2handedwclass: Weapon class for animation. Unimportant for item generation.
• component: Unimportant for item generation.
• hit class: Unimportant for item generation.
• invwidth: Width of the item in the inventory.
• invheight: Height of the item in the inventory.
• stackable: 1 for stackable weapons (throwing).
• minstack-maxstack: The range of quantity of items of this type in on stack.
• spawnstack: Quantity of items of this type in on stack upon founding.
• flippyfile, invfile, uniqueinvfile, setinvfile: Graphics files for the weapon.
• hasinv: 1 for socketable weapons.
• gemsockets: Maximum possible number of sockets in the weapon.
• gemapplytype: Item class for gems and runes. 0 for all weapons.
• special: Unimportant for item generation.
• useable: 1 for items, that you may use (e.c. town portal scroll). 0 for all weapons.
• dropsound, dropsfxframe, usesound: Sound-related information. Unimportant for item generation.
• unique: 1 for special quest items.
• transparent, transtbl: Not used.
• quivered: 1 for weapons, that need ammo.
• lightradius, belt, quest, questdiffcheck, missiletype: Unimportant for item generation.
• durwarning: Id of low durability warning icon.
• qntwarning: Id of low quantity warning icon.
• gemoffset: Unimportant for item generation.
• bitfield1: Weapon material code (is used in golem creation and rack drop checks).
• CharsiMin (and all other *Min fields): Should be minimal quantity of the item in vendor's price list, but isn't used (see chapter 12).
• CharsiMax (and all other *Max fields): If CharsiMax>0 then she can sell this item (see chapter 12).
• CharsiMagicMin (and all other *MagicMin fields): Should be minimal quantity of the item in vendor's price list, but isn't used (see chapter 12).
• CharsiMagicMax (and all other *MagicMax fields): If CharsiMagicMax>0 then she can sell this item (see chapter 12).
• CharsiMagicLvl (and all other *MagicLvl fields): If ilvl>=CharsiMagicLvl then she can sell this item (see chapter 12).

Source Art, Game Art, Transform, InvTrans, SkipName: Unimportant for item generation.

• NightmareUpgrade: Item code for selling by Nightmare difficulty vendors, "xxx" for items, that don't get upgrade (see Chapter 12).
• HellUpgrade: Item code for selling by Hell difficulty vendors, "xxx" for items, that don't get upgrade (see Chapter 12).
• Nameable: 1 for items that may be personalized by Anya's quest reward.
• PermStoreItem: Unimportant for item generation.

armor.txt

This is a file similar to weapons.txt.

• name: The name of the weapon as it appear in the game.
• version: 0 for Classic, 100 for Lod.
• compactsave: Unimportant for item generation.
• rarity: The rate of dropping the armor from weapon racks.
• spawnable: 0 for items, that cannot be generated (except special cases like quests), 1 for others.
• minac-maxac: Defence range.
• absorbs: Not used. Unimportant for item generation.
• speed: Run/walk speed penalty.
• reqstr: Strength required.
• block: Base chance to block.
• durability: Base durability.
• nodurability: 1 for indestructible armors.
• level: Quality Level.
• levelreq: Character level required.
• cost: Base weapon cost.
• gamble cost: Gambling cost.
• code: Internal item name.
• namestr: Reference to the table, contained correct name of the item.
• magic lvl: Magic Level (see chapter 11 and chapter 22).
• auto prefix: The code number of prefix, that always occurs on the armor (like poison damage on heads).
• alternategfx, OpenBetaGfx: Unimportant for item generation.
• normcode: Code of normal version of the armor.
• ubercode: Code of exceptional version of the armor.
• ultracode: Code of elite version of the armor.
• spelloffset, component: Unimportant for item generation.
• invwidth: Width of the item in the inventory.
• invheight: Height of the item in the inventory.
• hasinv: 1 for socketable armors.
• gemsockets: Maximum possible number of sockets in the armor.
• gemapplytype: Item class for gems and runes. 1 for headgear and body armor, 2 for shields.
• flippyfile, invfile, uniqueinvfile, setinvfile: Graphics files for the armor.
• rArm, lArm, Torso, Legs, rSPad, lSPad: Types of used graphics files.
• useable: 1 for items, that you may use (e.c. Town portal scroll). 0 for all armors.
• throwable: Not used.
• stackable: 1 for stackable items (not used for armors).
• minstack-maxstack: The range of quantity of items of this type in on stack (not used for armors).
• type, type2: Item type code, the index of respective raw in itemtypes.txt file.
• dropsound, dropsfxframe, usesound: Sound-related information. Unimportant for item generation.
• unique: 1 for special quest items.
• transparent, transtbl: Not used.
• quivered: 1 for weapons that need ammo (not used for armors).
• lightradius, belt, quest, questdiffcheck, missiletype: Unimportant for item generation.
• durwarning: Id of low durability warning icon.
• qntwarning: Id of low quantity warning icon (not used for armors).
• mindam-maxdam: Damage range for smite or kick.
• StrBonus: Strength bonus for kick damage. Enhanced damage percent=Strength*StrBonus/100.
• DexBonus: Dexterity bonus for kick damage. Enhanced damage percent=Dexterity*DexBonus/100.
• gemoffset: Unimportant for item generation.
• bitfield1: Armor material code (is used in golem creation and rack drop checks).
• CharsiMin (and all other *Min fields): Should be minimal quantity of the item in vendor's price list, but isn't used (see chapter 12).
• CharsiMax (and all other *Max fields): If CharsiMax>0 then she can sell this item (see chapter 12).
• CharsiMagicMin (and all other *MagicMin fields): Should be minimal quantity of the item in vendor's price list, but isn't used (see chapter 12).
• CharsiMagicMax (and all other *MagicMax fields): If CharsiMagicMax>0 then she can sell this item (see chapter 12).
• CharsiMagicLvl (and all other *MagicLvl fields): If ilvl>=CharsiMagicLvl then she can sell this item (see chapter 12).
• Source Art, Game Art, Transform, InvTrans, SkipName: Unimportant for item generation.
• NightmareUpgrade: Item code for selling by Nightmare difficulty vendors, "xxx" for items, that don't get upgrade (see Chapter 12).
• HellUpgrade: Item code for selling by Hell difficulty vendors, "xxx" for items, that don't get upgrade (see Chapter 12).
• mindam, maxdam: Not used.
• Nameable: 1 for items that may be personalized by Anya's quest reward.

Misc.txt

This file is similar to weapons.txt and armor.txt, but contains information about all items, that are neither weapon nor armor.

• name, *name: The name of the item as it appears in the game.
• szFlavorText, compactsave: Unimportant for item generation.
• version: 0 for Classic, 100 for Lod.
• level: Quality Level.
• levelreq: Character level required.
• rarity: The rate of dropping the item from different objects (e.c. book shelves).
• spawnable: 0 for items, that cannot be generated (except special cases like quests), 1 for others.
• speed: Not used for misc items.
• nodurability: 1 for indestructible items.
• cost: Base item cost.
• gamble cost: Gambling cost.
• code: Internal item name.
• alternategfx: Unimportant for item generation.
• namestr: Reference to the table, contained correct name of the item.
• component: Unimportant for item generation.
• invwidth: Width of the item in the inventory.
• invheight: Height of the item in the inventory.
• hasinv: 1 for socketable items.
• gemsockets: Maximum possible number of sockets in the item (not used for misc items).
• gemapplytype: Item class for gems and runes (not used for misc items).
• flippyfile, invfile, uniqueinvfile: Graphics files for the item.
• special: Not used.
• Transmogrify, TMogType, TMogMin, TMogMax: Unimportant for item generation.
• useable: 1 for items, that you may use (e.c. Town portal scroll). 0 for all others.
• throwable: Not used.
• type, type2: Item type code, the index of respective raw in itemtypes.txt file.
• dropsound, dropsfxframe, usesound: Sound-related information. Unimportant for item generation.
• unique: 1 for special quest items.
• transparent, transtbl: Not used.
• lightradius, belt: Unimportant for item generation.
• autobelt: 1 for items that automatically get placed on the belt.
• stackable: 1 for stackable items.
• minstack-maxstack: The range of quantity of items of this type in on stack.
• spawnstack: Quantity of items of this type in on stack upon founding.
• quest: >0 for quest items. Unimportant for item generation.
• questdiffcheck: Unimportant for item generation.
• missiletype, spellicon: Not used.
• pSpell, state, cstate1, cstate2, len: Unimportant for item generation.
• stat1, stat2, stat3: Effect of usable item. E.c. life restore for life potion.
• calc1, calc2, calc3: The value for effect of usable item. E.e. 100% life and mana for full * rejuvenation potion.
• spelldesc, spelldescstr, spelldesccalc: Used to refer to description of item effect.
• durwarning: Id of low durability warning icon.
• qntwarning: Id of low quantity warning icon.
• gemoffset: Unimportant for item generation.
• BetterGem: The code of gem for upgrade with cube or shrine.
• bitfield1: Item material code (is used in golem creation and rack drop checks).
• CharsiMin (and all other *Min fields): Should be minimal quantity of the item in vendor's price list, but isn't used (see chapter 12).
• CharsiMax (and all other *Max fields): If CharsiMax>0 then she can sell this item (see chapter 12).
• CharsiMagicMin (and all other *MagicMin fields): Should be minimal quantity of the item in vendor's price list, but isn't used (see chapter 12).
• CharsiMagicMax (and all other *MagicMax fields): If CharsiMagicMax>0 then she can sell this item (see chapter 12).
• CharsiMagicLvl (and all other *MagicLvl fields): If ilvl>=CharsiMagicLvl then she can sell this item (see chapter 12).
• Source Art, Game Art, Transform, InvTrans, SkipName: Unimportant for item generation.
• NightmareUpgrade: Item code for selling by Nightmare difficulty vendors, "xxx" for items, that don't get upgrade (see Chapter 12).
• HellUpgrade: Item code for selling by Hell difficulty vendors, "xxx" for items, that don't get upgrade (see Chapter 12).
• mindam, maxdam: Not used.
• PermStoreItem: 1 for items, that always available in stores.
• multibuy: 1 for items, that may be bought with Shift+Click (Multiple Buy function).
• Nameable: 1 for items that may be personalized by Anya's quest reward.
• *eol: Not used (however "eol" is usually End Of Line in programming).

4.7. ItemTypes.txt

This file describes basic item types, like a ring, a melee weapon, a bow.

• ItemType: The name of the item type for users.
• Code: The name of the item type for references from other files.
• Equiv1, Equiv2: Equivalent item types, i.e. codes of types, that include this item type. Eg. Throwing Knife is included in Knife item type.
• Repair: 1 for types, whose items may be repaired.
• Body, BodyLoc1, BodyLoc2: Location on player body. Unimportant.
• Shoots: Ammo type for weapons, that need them.
• Quiver: Type of ammo for item types, that are ammo.
• Throwable: 1 for throwable item types.
• Reload: 1 for item types, that reloads ammo from inventory (like crossbows and bows).
• ReEquip: 1 for item types, that are automatically equipped from inventory after running out (like throwing potions).
• AutoStack: 1 for stackable items that are automatically organized in stacks when you pick them (like keys).
• Magic: 1 for items that can be magic.
• Rare: 1 for items that can be rare.
• Normal: 1 for items that can be normal quality.
• Charm: 1 for charms.
• Gem: 1 for gems.
• Beltable: 1 for items, that you may put on your belt.
• MaxSock1: Maximum socket number for Ilvl<=25.
• MaxSock25: Maximum socket number for Ilvl<=40.
• MaxSock40: Maximum socket number for Ilvl>40.
• TreasureClass: 1 for item types, that gets automatic Treasure Classes. E.e. Weap87, Armo03.
• Rarity: Item drop probability. It is used for automatic Treasure Classes (see TreasureClassEx.txt description in chapter 4.1).
• StaffMods: The type of sfaffmods, that are generated on the item type (see chapter 11 for description of stuffmods).
• CostFormula: Unimportant.
• Class: Class requirement.
• VarInvGfx, InvGfx1, InvGfx2, InvGfx3, InvGfx4, InvGfx5, InvGfx6: Some unimportant graphics information.
• StorePage: The type of page in stores for selling this item type.
• *eol: Not used (however "eol" is usually End Of Line).

4.8. itemratio.txt

This is the most important file for determining quality of item. First, coverage of the fields, then an explanation of the quality calculation mechanics.

• Function: The description of the line.
• Version: 0 for Classic, 1 for Lod.
• Uber: 1 for exceptional and elite items, 0 for normal items.
• Class Specific: 1 for class specific items, 0 for all others.
• Unique: Basic chance for unique items (1:Unique).
• UniqueDivisor: The value for modifying basic chance for unique items (see description below).
• UniqueMin: Minimum value in calculating unique chance.
• Rare: Basic chance for rare items.
• RareDivisor: The value for modifying basic chance for rare items.
• RareMin: Minimum value in calculating rare chance.
• Set: Basic chance for set items.
• SetDivisor: The value for modifying basic chance for set items.
• SetMin: Minimum value in calculating set chance.
• Magic: Basic chance for magic items.
• MagicDivisor: The value for modifying basic chance for magic items.
• MagicMin: Minimum value in calculating magic chance.
• HiQuality: Basic chance for high quality items.
• HiQualityDivisor: The value for modifying basic chance for high quality items.
• Normal: Basic chance for normal quality items.
• NormalDivisor: — the value for modifying basic chance for normal quality items.

As you see the itemratio.txt file contains two rows for Classic mode and four rows for LoD mode. The two rows for Classic mode include the raw for normal and the raw for exceptional items in this order. The four rows for LoD mode include: 1) the raw for non-class specific normal items, 2) the raw for non-class specific exceptional and elite items, 3) the raw for class specific normal items and 4) he raw for class specific exceptional and elite items in this order.

The game selects correct raw using Version, Uber and Class Specific fields before starting the calculations.

The game selects quality for an item only when it already knows its item level and item type. It does the check for unique quality first. If it is successful it stops the algorithm and generates unique item or triple durability rare (or magic/normal item if this item type cannot be rare). If unique check is failed, the game makes set check by the same manner, then rare check, then magic check, then normal check, until some check will show success. If all checks fall it will generate low quality item.

Here is quality check algorithm:

1) Find proper line in itemratio.txt.
2) Chance = (BaseChance - ((ilvl-qlvl)/Divisor)) * 128
3) if (we check for unique, set or rare quality) EffectiveMF=MF*Factor/(MF+Factor) else EffectiveMF=MF
4) Chance= Chance* 100/(100+ EffectiveMF).
5) if (Chance 6) FinalChance=Chance-(Chance*QualityFactor/1024)
7) If (RND[ FinalChance ]<128) return Success
else return Fail

• BaseChance: The value from Unique, Rare, Set, Magic, HiQuality and Normal fields of itemratio.txt.
• ilvl: Item Level, usually ilvl=mlvl.
• qlvl: Quality level of item type.
• Divisor: The value from UniqueDivisor, RareDivisor, SetDivisor, MagicDivisor, HiQualityDivisor and NormalDivisor fields of itemratio.txt.
• MinChance: The value from UniqueMin, RareMin, SetMin, MagicMin fields of itemratio.txt. For high quality and Normal items MinChance=0.
• 'QualityFactor: The value from Unique, Set, Rare, Magic fields of TreasureClassEx.txt file for TC of the monster, that dropped this item.

See chapter eight for more discussion of quality selection mechanics.

Area, monster and item levels

I'm sorry if you find above information a bit hard and huge, — it is needed for you if you want to know everything about item drop process. Now we will learn something more interesting.

How does the game calculates levels of monsters when it creates the map?

In normal difficulty all normal monsters have fixed levels, that may be found in monstats.txt file. In Nightmare and Hell difficulties all normal monsters have levels equal to area levels, where they are placed.

Area levels can be found in Levels.txt file. Online list here. Champions get +2 bonus to their levels. Unique monsters and their minions get +3 bonus to their levels.

There are a few exceptions from this rule, though. Bosses, monsters that have boss=1 in monstats.txt file, have fixed level, stated in monstats.txt file, and don't get level upgrades. Here is their full list:

Id	NameStr	Level	Level(N)	Level(H)
andariel	Andariel	12	49	75
duriel	Duriel	22	55	88
radament	Radament	16	49	83
mephisto	Mephisto	26	59	87
diablo	Diablo	40	62	94
summoner	Summoner	18	55	80
izual	Izual	29	60	86
bloodrave	Bloodraven	10	43	88
griswold	Griswold	5	39	84
nihlathakboss	NIhlathak	65	70	92
baalcrab	Baal	60	75	99
putriddefiler1	Putrid Defiler	35	61	80
putriddefiler2	Wretched Defiler	37	62	81
putriddefiler3	Fetid Defiler	38	63	82
putriddefiler4	Rancid Defiler	39	64	83
putriddefiler5	Rank Defiler	40	65	84

• All Uber Bosses are level 110.
• Items, that are dropped by monsters have Item Levels equal to Monster Levels.

TC Selection and Number of Dropped Items

This is covered in detail in chapter 4.1. Here's a more text-based explanation, by Thrugg.

First is to know what TC a creature is supposed to drop from. For that you need to look up monstats.txt. This lists every monster in the game. Find the one you want (can be non trivial because they use tags which are not the same as the display names in game). Moon Lords are bloodlord5, as it happens. Scroll way over to the right end of the row, and you will see a whole bunch of TCs listed. These are, respectively, the TCs dropped by regular, champion and unique versions of the monster in each of normal, NM and Hell.

That's step 1 :) Next, back to TreasureClassEx.txt we go. In normal you just look up directly the TC and off you go, but in NM and Hell we have "TC upgrades". This is what the two columns that I haven't explained yet are for - "group" and "level". In NM or Hell, if a monster's level is higher than the level of his base TC, and there is another TC in the same group which is higher level but still equal to or less than his monster level, it will upgrade to that TC.

After you found the line in TreasureClassEx.txt file, that describe the drops of that monster you may calculate the number of his drops and types of dropped items. The game takes several picks from given TC. The number of picks stored in Picks column of TreasureClassEx.txt file. Typically all normal monsters have one pick. Every pick has chance for no dropping item at all.

When you play a multiplayer game, you have the total number of people in the game, say N.

All monsters get HP and exp multiplied by (N+1)/2. This is well known and also doesn't matter whether the players are partied, close by, whatever.

If you are playing off-realm you can also use /players X to raise the number of players to X > N. Then the HP and exp will scale up further to (X+1)/2 as you would expect.

Drops, however, are not the same. When you kill a monster in a multiplayer game, the game calculates a number to use as the nodrop exponent. This is not simply N.

• It counts 1 for you, the killing player.
• It counts 1 more for each player that is (a) partied with you and (b) within two screens of you.
• It counts 0.5 for each other player, either unpartied or far away.
• It rounds the final total down.

So, if you sneak into a full public game on the realms and don't party up but go MFing on your own, you actually only get a nodrop exponent of 4 (1 for you, 3 for the 7 unpartied players rounded down), while the other partied guys are getting an exponent of 7 (7 people in their party, and you rounded down to 0). Even though all of you are killing p8 monsters with their 4.5x HP. It is one of Blizzard's many measures to encourage party play.

You have your nodrop number (e.g. for Meph, this is 15) and your total of other drops (for Meph this is 65). This means the total ratio of nodrops in solo play is 15/(15+65) = 15/80 = ~19%.

You then apply your nodrop exponent (call it n) like this:

• new nodrop rate = (base nodrop rate)^n
• new nodrop number = new nodrop rate / (1 - new nodrop rate) * total drops, rounded down.

For example, Meph, nodrop exponent = 1

• new nodrop rate = (15/80)^1 = 15/80
• new nodrop number = 15/80 / (1 - 15/80) * 65 = 15/65 * 65 = 15 (just showing you that it works even for n=1)

Meph, nodrop exp = 2

• new nodrop rate = (15/80)^2 = 0.03515625
• new nodrop number = 0.03515625 / (1 - 0.03515625) * 65 = 0.036437 * 65 = 2 after rounding.

So with exponent = 2, Meph is already only missing drops 2/67 of the time.

Meph, nodrop exp = 3

• new nodrop rate = (15/80)^3 = 0.00659
• new nodrop number = 0.00659 / (1 - 0.00659) * 65 = 0.00664 * 65 = 0 after rounding.

So with exponent = 3, Meph is always dropping in full.

It is unfortunately extremely hard to test this empirically. Enough weird stuff happens that also seem to hide drops, plus Meph gets 7 drop chances and only 6 items can drop, that it is too hard to tell 2/67 apart from 0. So it could actually be that all this time we've been running Meph at players3 in SP to get full drops when really we are just getting exp=2 drops — you'd need to run him at players5 to get guaranteed full drops.

Extra players added using the /players command only count as unpartied players. This makes no difference to what we already knew for monster HP and XP. It does change what we thought was happening with drops. Unpartied players count as halves rounded down. So, when using the Atma drop calculator, you need to translate your /players setting into the number you put into the Players field:

• 1 or 2 -> 1
• 3 or 4 -> 2
• 5 or 6 -> 3
• 7 or 8 -> 4

This affects all monsters, not just Mephisto, although for unique monsters like Pindle and random bosses that have fixed drops, it won't actually change any numbers.

It should also be noted that the things you "know" are still mostly true. You can keep running Meph on p3. In retrospect I always wondered why people ran him on p3 instead of p2, when the difference in drops is so tiny. Well, it turns out that running at p3 is actually what I thought was p2, and p2 is no different than p1, so now it makes sense. You may still see a 5 drop every now and then at p3, but not often enough that it is worth going higher.

Ultimately, if you are MFing, there is rarely a reason to use an even number setting. The only difference between an even number and the number one lower is slightly more exp, but only one-for-one with the increased HP. So your drops per HP are lower and exp per HP is the same. For fast levelling, when all you care about is the most exp per monster you can get, p8 is still worthwhile.