Diablo 2 Guide: Calculating Poison Damage v1.10

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.

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.

DamageLength
PointsBitsSecondsFrames
1256125

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: 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).

Poison damage from multiple attacks doesn’t stack. If a target is already poisoned, then the rate and length of that poison will be overwritten by that of any subsequent attack which has an equal or greater rate. Rates are compared after all modifiers have been applied.

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 of poison damage is applied per frame: 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 CharmDisplayed damageBit rateFrames
MinMax
Toxic Small Charm100 Poison Damage Over 5 Seconds205205125
Small Charm of Anthrax50 Poison Damage Over 6 Seconds8686150
Toxic Small Charm of Anthrax313 Poison Damage Over 11 Seconds291291275

Displayed damage is rounded to the nearest point, although it should always be rounded down. When multiple items applying poison damage are equipped, then the rates are added and the lengths are averaged.

ItemDisplayed damageBit rateFrames
MinMax
Toxic Small Charm of Anthrax313 Poison Damage Over 11 Seconds291291275
Blackbog’s Sharp Cinquedeas488 Poison Damage Over 10 Seconds500500250
Perfect Emerald100 Poison Damage Over 7 Seconds143143179
Total934934704
Frames= [704/3]
= 234

Thus 853 poison damage is applied over 9.36 seconds (934*234/256 over 234/25). Bits and frames are the smallest units of measurement, and 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.

ERROR: Length is calculated differently when multiple items applying poison damage are used with skills that apply less than 100% weapon damage:

Poison length = [sum of lengths / (sources – 1) ]

  • Multiple Shot
  • Strafe
  • Blade Fury using one-handed weapon

Poison length = sum of lengths

  • Blade Sentinel
  • Blade Fury using two-handed weapon
  • Poison damage 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. 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.

SkillBit rateFramesSynergy
/Level12-89-1617-2223-28>2812+Skill+%
Poison Javelin (Pn)Min

Max

32

48

+16

+16

+32

+36

+48

+52

+64

+68

+96

+84

200+50Pe12
Plague Javelin (Pe)Min

Max

80

128

+48

+48

+96

+96

+160

+160

+320

+320

+480

+480

75+10Pn10
Poison Dagger (PD)Min

Max

36

80

+20

+20

+30

+30

+40

+40

+46

+46

+52

+52

50+10PE

PN

20

20

Poison Explosion (PE)Min

Max

128

384

+32

+32

+64

+64

+96

+96

+128

+128

+160

+160

50+10PD

PN

15

15

Poison Nova (PN)Min

Max

256

464

+64

+64

+96

+96

+144

+144

+224

+224

+256

+256

50PD

PE

10

10

Poison Creeper (PC)Min

Max

12

16

+7

+7

+12

+12

+15

+15

+17

+17

+19

+19

100
RabiesMin

Max

48

112

+32

+32

+40

+40

+56

+56

+88

+88

+128

+128

100+10PC18
VenomMin

Max

1,536

2,048

+384

+384

+512

+512

+640

+640

+768

+768

+896

+896

10

ERROR: Level >36 Poison Javelin displays higher minimum than maximum damage because the minimum bit rate added per level for level >28 is higher than the maximum bit rate added. When this occurs, the minimum damage becomes the maximum and the maximum damage becomes the minimum.

Level 30 Poison Dagger applies the following:

Frames= 50+(10*(30-1))
= 50+290
= 340
Min bit rate= 36+(20*7)+(30*8)+(40*6)+(46*6)+(52*2)
= 36+140+240+240+276+104
= 1,036
Min damage= 1,036*340/256
= 1,375
Max bit rate= 80+(20*7)+(30*8)+(40*6)+(46*6)+(52*2)
= 80+140+240+240+276+104
= 1,080
Max damage= 1,080*340/256
= 1,434

Thus 1,375-1,434 Poison Damage Over 13.6 Seconds is displayed. Fully synergised level 30 Poison Dagger (20 points each in Poison Explosion and Nova) has +800% (20*(20+20)) applied to its rate:

Min bit rate= 1,036*(100+800)/100
= 1,036*9
= 9,324
Min damage= 9,324*340/256
= 12,383
Max bit rate= 1,080*(100+800)/100
= 1,080*9
= 9,720
Max damage= 9,720*340/256
= 12,909

Thus 12,383-12,909 Poison Damage Over 13.6 Seconds is 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.

SourceDisplayed damageBit rateFrames
MinMax
Toxic Small Charm of Anthrax313 Poison Damage Over 11 Seconds291291275
Blackbog’s Sharp Cinquedeas488 Poison Damage Over 10 Seconds500500250
Perfect Emerald100 Poison Damage Over 7 Seconds143143179
Level 30 Poison Dagger12,383-12,909 Poison Damage Over 13.6 Seconds9,3249,720340
Total10,25810,6541,044
Frames= [1,044/3]
= 348
Min damage= 10,258*348/256
= 13,944
Max damage= 10,654*348/256
= 14,482

Thus 13,944-14,482 poison damage is applied 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, its 10 frame length overrides those of any items.

SourceDisplayed damageBit rateFrames
MinMax
Toxic Small Charm of Anthrax313 Poison Damage Over 11 Seconds291291275
Blackbog’s Sharp Cinquedeas488 Poison Damage Over 10 Seconds500500250
Perfect Emerald100 Poison Damage Over 7 Seconds143143179
Level 15 Venom305-325 Poison Damage Over 0.4 Seconds7,8088,32010
Total8,7429,25410
Min damage= 8,742*10/256
= 341
Max damage= 9,254*10/256
= 361

Thus just 341-361 poison damage is applied over 0.4 (10/25) 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 Venom effectively creates a single source which sums the rates of Venom and items but which only applies for Venom’s length, the length is the sum of the skill length and that of Venom.

SourceDisplayed damageBit rateFrames
MinMax
Toxic Small Charm of Anthrax313 Poison Damage Over 11 Seconds291291275
Blackbog’s Sharp Cinquedeas488 Poison Damage Over 10 Seconds500500250
Perfect Emerald100 Poison Damage Over 7 Seconds143143179
Level 30 Poison Dagger12,383-12,909 Poison Damage Over 13.6 Seconds9,3249,720340
Level 15 Venom305-325 Poison Damage Over 0.4 Seconds7,8088,32010
Total18,06618,974350
Min damage= 18,066*350/256
= 24,699
Max damage= 18,974*350/256
= 25,941

Thus 24,699-25,941 poison damage is applied over 14 (350/25) seconds. Classes other than the Assassin can gain the ability to cast Venom by equipping certain items, which allow it to be cast by various methods.

ItemSourceDuration (seconds)Bit rateFrames
MinMax
Arachnid Mesh Spiderweb SashLevel 3 Venom (11 Charges)1282,3042,81610
Andariel’s Visage DemonheadLevel 3 Venom (20 Charges)1282,3042,81610
Treachery ‘ShaelThulLem’ Armor25% Chance to Cast Level 15 Venom on Striking1767,8088,32010
Grief ‘EthTirLoMalRal’ Sword/Axe35% Chance to Cast Level 15 Venom on Striking1767,8088,32010
Dragon ‘SurLoSol’ Armor/Shield20% Chance to Cast Level 18 Venom When Struck1889,60010,11210
Rainbow Facet Jewel100% Chance to Cast Level 23 Venom When You Level-up20812,92813,44010

+% Poison Skill Damage

+% Poison Skill Damage 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 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. For more details about the mechanics of each skill, see the individual skill descriptions.

SkillPoint of application
Poison JavelinJavelin: throwing

Clouds: creation

Plague JavelinJavelin: throwing

Clouds: creation

Poison DaggerStriking
Poison ExplosionCasting
Poison NovaCasting
RabiesBite: striking

Contagion: creation

VenomCasting

Equipping Trang-Oul’s Claws Heavy Bracers applies +25% PSD to level 15 Venom when cast:

Min bit rate= 7,808*(100+25)/100
= 7,808*1.25
= 9,760
Max bit rate= 8,320*(100+25)/100
= 8,320*1.25
= 10,400
SourceDisplayed damageBit rateFrames
MinMax
Toxic Small Charm of Anthrax313 Poison Damage Over 11 Seconds291291275
Blackbog’s Sharp Cinquedeas488 Poison Damage Over 10 Seconds500500250
Perfect Emerald100 Poison Damage Over 7 Seconds143143179
Level 15 Venom305-325 Poison Damage Over 0.4 Seconds9,76010,40010
Total10,69411,33410
Level 30 Poison Dagger12,383-12,909 Poison Damage Over 13.6 Seconds9,3249,720340

+25% PSD is now applied:

Min bit rate= (10,694*(100+25)/100)+(9,324*(100+25)/100)
= (10,694*1.25)+(9,324*1.25)
= 13,367+11,655
= 25,022
Min damage= 25,022*(340+10)/256
= 34,209
Max bit rate= (11,334*(100+25)/100)+(9,720*(100+25)/100)
= (11,334*1.25)+(9,720*1.25)
= 14,167+12,150
= 26,317
Max damage= 26,317*(340+10)/256
= 35,980

Thus 34,209-35,980 poison damage is applied over 14 (350/25) seconds. +% PSD can only be found on the following items:

Item+% PSD
Rainbow Facet Jewel3-5
Trang-Oul’s Claws Heavy Bracers25
Bramble ‘RalOhmSurEth’ armor25-50

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 capped at PR 95%). Lower Resist (LR) applies PR -%, although it’s applied at 1/5 effectiveness against Immune to Poison monsters: 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.

25,022-26,317 bit rate for 350 frames results in 34,209-35,980 poison damage being applied over 14 seconds to a target with PR 0%. PR 50% would halve the rate, but casting level 10 LR (PR -55%) results in the following:

Min bit rate= 25,022*(100-(50-55))/100
= 25,022*1.05
= 26,273
Min damage= 26,273*350/256
= 35,920
Max bit rate= 26,317*(100-(50-55))/100
= 26,317*1.05
= 27,632
Max damage= 27,632*350/256
= 37,778

Thus 35,920-37,778 poison damage is applied over 14 (350/25) seconds. 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, once poison has been applied its rate and length remain unchanged, even if the monster becomes Immune to Poison again.

-% Enemy Poison Resistance

-% Enemy Poison Resistance (EPR) reduces a target’s poison resistance 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 >99%, 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).

-% 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.

25,022-26,317 bit rate for 350 frames results in 34,209-35,980 poison damage being applied over 14 seconds to a target with PR 0%. PR 110% makes a monster Immune to Poison, but casting level 10 LR (PR -11%) breaks that immunity and, combined with Trang-Oul’s Wing Cantor Trophy’s -25% EPR partial set bonus when equipping two other items from Trang-Oul’s Avatar, results in the following:

Frames= 350*(100-(0-25))/100
= 350*1.25
= 437
Min bit rate= 25,022*(100-(110-11-25))/100
= 25,022*0.26
= 6,505
Min damage= 6,505*437/256
= 11,104
Max bit rate= 26,317*(100-(110-11-25))/100
= 26,317*0.26
= 6,842
Max damage= 6,842*437/256
= 11,679

Thus 11,104-11,679 poison damage is applied over 17.48 (437/25) seconds. -% EPR can only be found on the following items:

Item-% EPR
Rainbow Facet Jewel3-5
Trang-Oul’s Wing Cantor Trophy (3 Items)25
Grief ‘EthTirLoMalRal’ Sword/Axe20-25
Death’s Web Unearthed Wand40-50

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 = [Rate*Frames/256]

Second = 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
BSkill rate
ISum of item rates
VVenom rate
MMastery (+X% Poison Skill Damage)M= (100+X)/100
SSynergy (+X% poison damage)S= (100+X)/100
RResistanceR= (100-X)/100
IfP >= 100 and P-(L/5) < 100
then X = P-(L/5)
else R = 0
IfP < 100
then X = Max(P-(L+E),-100)
PPoison Resist X%P = X
LLower Resist (Poison Resist -X%)L = X
E-X% Enemy Poison ResistanceE = 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
FFrames
Items
Items + Skill
Items + Venom
Skill + Venom
F = sum of item lengths/number of items
F = (skill length + sum of item lengths)/number of items
F = Venom length
F = skill length + Venom length
RResistanceR = (100-X)/100
IfP < 100
then X = Max(P-E,-100)
else F = 1
PPoison Length Reduced by X%P = X
E-X% Enemy Poison ResistanceE = X

ERROR: Length is calculated differently when multiple items applying poison damage are used with skills that apply less than 100% weapon damage:

Poison length = [sum of lengths / (sources – 1) ]

  • Multiple Shot
  • Strafe
  • Blade Fury using one-handed weapon

Poison length = sum of lengths

  • Blade Sentinel
  • Blade Fury using two-handed weapon

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