Some (if not all) of what follows may already be known, but to the best of my knowledge it hasn't all been collected in one place on this site. Bkelly's The Tao of Poison was an excellent source of information about poison damage for v1.09, but there are a number of changes in Diablo II: Lord of Destruction v1.10+ and the Tao hasn't been updated.
I've also posted Poison damage calculator.xls, a Microsoft Excel worksheet, in the Diablo Files forum of the Diablo III Community Forums. Even if you know how to calculate poison damage, this should make it easier. :)
Diablo II Strategy Guide Info:
- Patch: v1.10
- Gametype: PvE/PvM and PvP
- Guide Topics: Poison damage and Baal
- Class: Amazon, Assassin, Barbarian, Druid, Necromancer, Paladin, Sorceress
- Author: onderduiker
- Related Article(s): Poison damage calculator.xls, The Tao of Poison
Introduction
While damage is displayed in points and length in seconds, both are calculated and applied using more precise units of measurement. Damage is calculated and applied in bits, and length in frames.
DAMAGE LENGTH Points Bits Seconds Frames ___________________________________ 1 256 1 25
Poison damage is displayed as the total damage applied over a length of time, but it's calculated by applying a bit rate (bit damage per frame) for a specified number of frames. For example, a Toxic Small Charm applies 205 bit rate for 125 frames, which is displayed as 100 Poison Damage Over 5 Seconds (205 * 125/256 over 125/25).
For simplicity's sake, rate can be expressed in poison damage per second and length in seconds, so a Toxic Small Charm applies 20 (100/5) poison damage per second for 5 seconds. The resulting calculations won't be entirely accurate, but should still give good approximations.
UPDATE 3 AUGUST 2009 When players, hirelings or pets apply poison to a poisoned monster, their poison is applied for one frame instead of the current poison: if their poison has an equal or greater rate, it then overwrites the current poison and it gets applied for its length; if their poison has a lower rate, the current poison then continues for its remaining length. Rates are compared after all modifiers have been applied.
When monsters apply poison to a poisoned player, hireling or pet, their poison is applied for one frame as well as the current poison: if their poison has an equal or greater rate, it then overwrites the current poison and it gets applied for its length; if their poison has a lower rate, the current poison then continues for its remaining length. Rabies and Poison Creeper can also apply additional frames of poison damage when applied to more than one monster.
A monster's damage regeneration is stopped if at least one bit (1/256 point) of poison damage is applied per frame (1/25 second): monsters won't turn green if less than one bit of poison damage is applied per frame. Poison damage can kill monsters, hirelings and pets but will only reduce players to 1 hit point (although poison damage from a subsequent attack would kill them if they remained on 1 hit point).
Items
If a single item has both a prefix and a suffix applying poison damage, then the rates and lengths of both are simply added.
SMALL CHARM DISPLAYED DAMAGE BIT RATE FRAMES
Min Max
____________________________________________________________________________________
Toxic Small Charm 100 Poison Damage Over 5 Seconds 205 205 125
Small Charm of Anthrax 50 Poison Damage Over 6 Seconds 86 86 150
Toxic Small Charm of Anthrax 313 Poison Damage Over 11 Seconds 291 291 275
Alternatively, a combined rate of (100/5) + (50/6) poison damage per second is applied for (5 + 6) seconds, resulting in approximately 312 poison damage over 11 seconds. The displayed damage is rounded to the nearest point, although it should actually be rounded down (that charm's poison damage wouldn't kill a monster with 313 hit points, although it would reduce it to 103/256 hit point).
When multiple items applying poison damage are equipped, then the rates are added and the lengths are averaged.
ITEM DISPLAYED DAMAGE BIT RATE FRAMES
Min Max
____________________________________________________________________________________
Toxic Small Charm of Anthrax 313 Poison Damage Over 11 Seconds 291 291 275
Blackbog's Sharp Cinquedeas 488 Poison Damage Over 10 Seconds 500 500 250
Perfect Emerald 100 Poison Damage Over 7 Seconds 143 143 179
____________________________________________________________________________________
TOTAL 934 934 704
The average length of these three items is 234 (704/3) frames, so 853 poison damage is applied over 9.36 seconds (934 * 234/256 over 234/25). Bits and frames are the smallest units of measurement, so calculations are rounded down to the nearest bit and frame. Gems, jewels and runes all count as separate items, even if they're socketed in a single item.
There's a bug when calculating poison length for skills that apply a fraction of weapon damage, namely Multiple Shot, Strafe and Blade Sentinel, Fury and Shield. Two items will apply poison damage over the sum of their lengths, while three or more items will just apply poison damage over the longest length of any of those items.
Skills
Poison damage skills add bit rate with every additional skill level. The bit rate added also increases beyond certain skill levels. Some skills also add length with every additional skill level, although the increase is linear. Others are synergised by other skills, which apply a percentage increase to bit rate dependent on the number of skill points invested in the synergy skill(s). Skill level is set at the point the player uses the skill, so adding or removing skill bonuses won't have any effect on rate or length if there's a delay between using the skill and applying the poison.
For example, level 30 Poison Dagger applies 1,036-1,080 bit rate for 340 frames, which displays as 1,375-1,434 Poison Damage Over 13.6 Seconds. Fully synergised (20 points each in Poison Explosion and Nova), +800% (20 * (20 + 20)) is applied to this rate, resulting in 9,324-9,720 bit rate for 340 frames and 12,383-12,909 Poison Damage Over 13.6 Seconds being displayed.
Skills and Items
Most skills are treated as separate sources of poison damage whose rates (and accompanying lengths) compete with those of other skills and items. However, Poison Dagger and the javelins (but not the clouds) of Poison and Plague Javelins combine the skill's rate with any item rates. Length is calculated by summing skill and item lengths and dividing by the number of items.
SOURCE BIT RATE FRAMES
Min Max
_________________________________________________
Three items 934 934 704
Level 30 Poison Dagger 9,324 9,720 340
_________________________________________________
TOTAL 10,258 10,654 1,044
10,258-10,654 bit rate is applied for 348 (1,044/3) frames, resulting in 13,944-14,482 poison damage over 13.92 (348/25) seconds.
If the only item used were Blackbog's Sharp Cinquedeas, 9,824-10,220 bit rate for 590 ((250 + 340)/1) frames would apply 22,641-23,553 poison damage over 23.6 (590/25) seconds. Although the rate is lower with only one item, the length can be significantly longer and results in far more damage from a single stab.
Venom
Venom's rate is applied to any weapon's attack made between its casting and expiration, and adds to any rate applied by items. However, this combined rate is only applied for Venom's 0.4 second (10 frame) length: item lengths become irrelevant.
SOURCE BIT RATE FRAMES
Min Max
_________________________________________________
Three items 934 934
Level 15 Venom 7,808 8,320 10
_________________________________________________
TOTAL 8,742 9,254 10
Level 15 Venom displays 305-325 Poison Damage Over 0.4 Seconds, and the rates of those three items only increase that to 341-361 poison damage over 0.4 seconds.
However, Venom's length does not override those of the skills Poison Dagger and Poison and Plague Javelins. Casting Venom can thus significantly increase the rate applied by these skills while not reducing length, since poison length is the sum of the skill's length and Venom's length.
SOURCE BIT RATE FRAMES
Min Max
_________________________________________________
Three items 934 934
Level 15 Venom 7,808 8,320 10
Level 30 Poison Dagger 9,324 9,720 340
_________________________________________________
TOTAL 18,066 18,974 350
Thus 24,699-25,941 poison damage is applied over 14 (350/25) seconds.
+% to Poison Skill Damage
+% to Poison Skill Damage (PSD) is gained by equipping certain items and applies a percentage increase to the rate, which is multiplicative with any synergies. It's also applied to the rate from items and Venom when applied with mêlée weapons, but not when applied with ranged weapons.
The point at which +% PSD is applied varies for each skill, although it is not applied to Poison Creeper.
SKILL APPLICATION
________________________________________________
Poison and Plague Javelins Javelin: Throwing
Clouds: Creation
Poison Dagger Striking
Poison Explosion Casting
Poison Nova Casting
Rabies Bite: Striking
Contagion: Creation
Venom Casting
Equipping Trang-Oul's Heavy Bracers applies +25% PSD to level 15 Venom when cast, resulting in 9,760-10,400 bit rate.
SOURCE BIT RATE FRAMES
Min Max
_________________________________________________
Three items 934 934
Level 15 Venom 9,760 10,400 10
_________________________________________________
TOTAL 10,694 11,334 10
+25% PSD is applied to Poison Dagger's rate, and since it's a mêlée attack it's also applied (separately) to the combined rate of the items and Venom.
SOURCE BIT RATE FRAMES
Min Max
_________________________________________________
Items and Venom 13,367 14,167 10
Level 30 Poison Dagger 11,655 12,150 340
_________________________________________________
TOTAL 25,022 26,317 350
This results in 34,209-35,980 poison damage over 14 seconds.
Lower Resist
A target's Poison Resist (PR) % reduces poison's rate, and PR 100+% makes a monster Immune to Poison (players and hirelings are normally limited to PR 75%, but can increase the limit to PR 95% with items and Antidote Potions). Lower Resist (LR) applies PR -%, although it's applied at 1/5 effectiveness against Immune to Poison monsters e.g. level 10 LR's PR -55% is reduced to PR -11% (55/5). PR -100% is the absolute minimum to which a target can be reduced, doubling the rate.
LR is applied when the target is poisoned, so it can be overwritten by another Curse immediately afterwards. Even if LR is required to break immunity (i.e. reducing PR 100+% to PR < 100%), once poison has been applied its rate and length remain unchanged, even if the monster displays 'Immune to Poison' again.
-% to Enemy Poison Resistance
-% to Enemy Poison Resistance (EPR) reduces a target's PR % like LR, but only if PR < 100% i.e. not Immune to Poison. However, unlike LR -% EPR also applies to length, effectively applying Poison Length Reduced (PLR) by -%.
Monsters have no PLR % so -% EPR increases poison length by the displayed amount, although -100% is the absolute minimum to which a target can be reduced, doubling the length. The only exceptions are the Ancients, whose equipment can spawn with PLR % suffixes. Talic and Korlic can spawn with PLR 100+%, which cannot be reduced by -% EPR. However, this doesn't result in effective immunity, since a frame of poison damage is still applied.
Players and hirelings are capped at PLR 75%, although the same difficulty penalties that apply to Resist % apply (-40% in Nightmare and -100% in Hell). PLR % will counter an opponent's -% EPR when duelling (and vice versa).
-% EPR is applied when the target is poisoned, like LR. Once poison has been applied its rate and length remain unchanged, so -% EPR can be removed afterwards without affecting damage or length.
Level 30 Poison Dagger (augmented by items, Venom and +% PSD) now applies 25,022-26,317 bit rate for 350 frames, resulting in 34,209-35,980 poison damage being applied over 14 seconds to a target with PR 0%. A combination of level 10 LR (PR -55%) and Trang-Oul's Wing Cantor Trophy's -25% EPR partial set bonus when equipping two other items from Trang-Oul's Avatar reduces that to PR -80%, increasing rate by 80%.
-25% EPR increases poison length by 25%, so 45,039-47,370 bit rate is applied for 437 (350 * 1.25) frames, resulting in 76,882-80,862 poison damage over 17.48 (437/25) seconds.
Calculation
This is a summary of all the individual steps in the calculation of poison damage outlined in the preceding sections. To express total damage in points applied over a length in seconds:
Points = [Bit Rate * Frames/256]
Seconds = Frames/25
Ideally damage is calculated measuring rate in bits and length in frames. It's also possible to calculate damage measuring rate in poison damage/second and length in seconds, which can be derived directly from displayed damage. However, the result will only be an approximation and rounding down should only be done at the end of the calculation for the maximum accuracy possible.
Rate = [([[B * S] * M] + [(I + [V*M]) * M]) * R]
[ ] Round down
B Skill rate
I Sum of item rates
V Venom rate
M Mastery (+X% to Poison Skill Damage) M = (100 + X)/100
S Synergy (+X% poison damage) S = (100 + X)/100
R Resistance R = (100 - X)/100
If P >= 100 and P - [L/5] < 100
then X = P - [L/5]
else R = 0
If P < 100
then X = Max(P - (L + E), -100)
P Poison Resist X% P = X
L Lower Resist (Poison Resist -X%) L = X
E -X% to Enemy Poison Resistance E = X
- If a single item has both a prefix and a suffix applying poison damage, then the rates and lengths of both are simply added.
- Gems, jewels and runes all count as separate items, even if they're socketed in a single item.
- Item and Venom rate are only added to the skill rates of Poison Dagger and the javelins (but not the clouds) of Poison and Plague Javelins.
- +% PSD isn't applied to item and Venom rate when applied by ranged attacks.
Frames = [F * R]
[ ] Round down
F Frames
Items F = sum of item lengths/number of items
Items + Skill F = (skill length + sum of item lengths)/number of items
Items + Venom F = Venom length
Skill + Venom F = skill length + Venom length
R Resistance R = (100 - X)/100
If P < 100
then X = Max(P - E, -100)
else F = 1
P Poison Length Reduced by X% P = X
E -X% to Enemy Poison Resistance E = X
- Item or Venom lengths are only added to the skill lengths of Poison Dagger and the javelins (but not the clouds) of Poison and Plague Javelins.
- There's a bug in the poison length calculation when using skills that apply a fraction of weapon damage, namely Multiple Shot, Strafe and Blade Sentinel, Fury and Shield. Two items will apply poison damage over the sum of their lengths, while three or more items will just apply poison damage over the longest length of any of those items.