Viper Strike

The thieves guilds of Oriath teach a wicked skill to all initiates - the feared Viper Strike. Employing the skill, a claw, dagger or sword user coats their weapon with deadly venom, a concoction so virulent it permanently marks any weapon it contacts. Once the toxin is applied, the weapon will poison any it strikes, burning deep into their veins, causing wracking, crippling pain. Additional hits will increase the concentration of the toxin, stacking it up to lethal levels quickly. Few have survived an assault of Viper Strike and those who have never forget the agony.

Skill Functions and Interactions

A viper strike does extra initial damage, and then also has a 50% chance per hit of adding a 'debuff' (a degen charge) which does DoT damage proportional to the size of the initial physical hit, and this debuff ticks off for the next 7 seconds by default. There is no upper limit to the number of debuffs that may be stacked; it is simply a function of attack speed and debuff duration.

Viper Strike damage is therefore driven by physical damage, with additional modifications from bonuses to Chaos and DoT damage.

Gem level progression

Template:GemLevelTable |- ! 1 | 1 || class="table-na" style="text-align: center; " | N/A || 5 || 0% || 70 |- ! 2 | 2 || class="table-na" style="text-align: center; " | N/A || 5 || 4% || 308 |- ! 3 | 4 || 16 || 5 || 8% || 2,560 |- ! 4 | 8 || 25 || 5 || 12% || 8,813 |- ! 5 | 12 || 33 || 5 || 16% || 22,895 |- ! 6 | 16 || 41 || 6 || 20% || 68,427 |- ! 7 | 21 || 52 || 6 || 24% || 150,439 |- ! 8 | 26 || 62 || 6 || 28% || 581,328 |- ! 9 | 32 || 75 || 6 || 32% || 566,989 |- ! 10 | 38 || 88 || 6 || 36% || 1,143,783 |- ! 11 | 42 || 96 || 7 || 40% || 1,426,490 |- ! 12 | 46 || 104 || 7 || 44% || 2,737,323 |- ! 13 | 49 || 111 || 7 || 48% || 3,289,072 |- ! 14 | 52 || 117 || 7 || 52% || 3,350,845 |- ! 15 | 55 || 123 || 7 || 56% || 9,936,192 |- ! 16 | 58 || 130 || 8 || 60% || 21,346,246 |- ! 17 | 61 || 136 || 8 || 64% || 50,693,883 |- ! 18 | 64 || 142 || 8 || 68% || 90,050,361 |- ! 19 | 66 || 146 || 8 || 72% || 147,034,294 |- ! 20 | 68 || 151 || 8 || 76% || class="table-na" style="text-align: center; " | N/A |- ! 21 | 68 || 151 || 9 || 80% || class="table-na" style="text-align: center; " | N/A |- ! 22 | 68 || 151 || 9 || 84% || class="table-na" style="text-align: center; " | N/A |- ! 23 | 68 || 151 || 9 || 88% || class="table-na" style="text-align: center; " | N/A |- ! 24 | 68 || 151 || || ||class="table-na" style="text-align: center; " | N/A |- ! 25 | 68 || 151 || || ||class="table-na" style="text-align: center; " | N/A |- ! 26 | 68 || 151 || || || class="table-na" style="text-align: center; " | N/A |}

Damage Formula

Character builds constructed around Viper Strike will want to optimize their damage output, and this involves striking a balance between physical damage, chaos and DoT bonuses. The formula which expresses how these different factors relate to overall VS damage is however not simple.

Since each hit has only a 50% chance to apply a DoT charge (official patch notes and some in-game language call this a 'debuff,' but visually it behaves much more like a charge of poison), the total damage output needs to take into account the fact that not every hit will be equal. The simplest unit of VS damage would involve two hits, one which sets a charge, and one which does not:

Hit 1: (VS Hit)

Hit 2: (VS Hit) + (VS DoT) * Duration

The total damage for this sequence is therefore:

Total Damage = 2 * (VS Hit) + (VS DoT) * Duration

The real complexity comes from what factors into the (VS Hit) and (VS DoT) terms. We'll get better insight into how the total damage depends on physical damage, chaos bonuses, and DoT bonuses if we can express these two different hits in terms of those factors.

VS Hit

The simplest of the two is the VS Hit. The Viper Strike gem brings a physical damage bonus, and then also applies 10% of this physical hit as chaos damage. This chaos damage is further modified by any chaos damage bonuses.

VS Hit = (Physical Hit) + 0.10 * (Physical Hit) * (1 + Chaos Bonus)

= (1.10 + 0.1 (Chaos Bonus)) * (Physical Hit)

Where Chaos Bonus is expressed in terms of a decimal (i.e. 10% is 0.10)

VS DoT

Each tick of each charge per second does chaos damage of 25% of the initial physical hit, which is then further modified by bonuses to chaos and DoT damage as follows:

VS DoT = 0.25 (Physical Hit) * (1 + Chaos Bonus) * (1 + DoT Bonus)

Note that each of our three basic damage sources - physical, chaos, and DoT - compound one another in this term multiplicatively. And yet passive node bonuses to each of these factors boosts them only additively. This means there will be diminishing returns to stacking just one of the bonuses in favor of the other two.

Total Damage in terms of 3 factors

Putting these two results back together again, in the two-hit sequence from above, we have:

Total Damage = 2 * (Physical Hit) * (1.10 + 0.1(Chaos Bonus)) + 0.25 (Physical Hit) * (1 + Chaos Bonus) (1 + DoT Bonus) * Duration

= (Physical Damage) * (2.20 + 0.2 (Chaos Bonus) + 0.25 (1 + Chaos Bonus) (1 + DoT Bonus)) * Duration

From this derived formula it can be determined at any stage whether a character would get more damage bang for their buck by investing in physical, chaos, or DoT bonuses. Physical damage is obviously the most dominant factor, but since many characters will often have a large degree of physical damage bonuses anyway, it's a legitimate question whether further (additive) boosts to physical damage would accomplish more than a new bonus to chaos or DoT bonuses. Here are a couple sample results from the above formula as rules of thumb:

• If the current physical damage bonus is 100%, and the current chaos (or DoT) bonus is 0%, then a 10% bonus to chaos damage (or DoT) would have roughly the same impact to total VS damage as a 10% bonus to physical damage
• If the current physical damage bonus is 200%, and the current chaos (or DoT) bonus is 0%, then a 10% bonus to chaos damage (or DoT) would have roughly the same impact to total VS damage as a 15% bonus to physical damage

Working out the numbers for other situations is left as an exercise for the reader

Quest reward

This skill can be gained as a reward for finishing quest:

• Mercy Mission in Act 1 (Normal), by Shadow
• Breaking Some Eggs in Act 1 (Normal), by Shadow, Ranger and Duelist
• The Caged Brute in Act 1 (Normal), by Ranger

Version history

Version	Changes
1.2.0	This skill now adds 10% of physical damage as Chaos Damage and has a 50% chance to deal 175% of the attack's damage as chaos damage over seven seconds. The effect duration won't be refreshed by new attacks, but there is no limit to how many Viper Strike debuffs an enemy can have.
1.0.3	Damage progression has been increased. It is now around 15% better at level 15 than it was in 1.0.2.
1.0.2b	Fixed a bug where area damage bonuses would not benefit Viper Strike when supported by .
1.0.2	Generic modifiers to damage dealt will now apply to damage over time that your character causes. Damage over time is not spell damage, nor attack damage, so modifiers specific to those types will not apply. Non-specific "increased damage" modifiers will apply to damage over time. Type-specific modifiers will apply as well. For example, "increased fire damage" modifiers will apply to fire damage over time. Viper Strike can be supported by , now that the damage penalty also applies.
0.9.13	Viper Strike is now 38% better at level 1 and 3% better at level 15.
0.9.12qq	From 0.35% attack speed per quality point to 0.5%.
0.9.12d	Fixed a server crash that could occur with Viper Strike.
0.9.5	Fixed Viper Strike so that damage from the degeneration is scaled properly for PvP.
0.9.4	Increased the damage.
0.9.2	Viper Strike does more damage at higher levels than before. Reduced maximum number of charges to 4.
0.9.1	Reduced Viper Strike duration at lower levels.