Viper build & guide (7.41)

Poison Attack

Intensifies Viper's venom, adding an effect to his normal attack that applies a stacking movement speed slow and magic resistance deduction while dealing damage over time. Stacks up to 6 times.

Aghanim's Shard: Increases max stacks, and causes Poison Attack to lower armor per stack and to affect buildings for reduced damage.

Nethertoxin

Viper releases a Nethertoxin at the targeted area. Units in that area take an increasing damage over time based on how long they remain in it. Units in it have their attack speed slowed.

Corrosive Skin

Viper exudes an infectious toxin that damages and slows the attack speed of any enemy that damages it in a 1200 radius. The acid exudate also increases Viper's resistance to magic.

Aghanim's Scepter: Corrosive Skin applies 4x the attack speed slow to enemies that are within 500 distance of Viper. Viper's Corrosive Skin Magic Resistance and Damage per Second are gradually increased while he is in Nethertoxin, up to 50% increased effect after 4s.

Nosedive

Viper slams into the ground, releasing a Nethertoxin and splattering each enemy in a 500 AoE for 4 seconds with the effect of Corrosive Skin.

Predator

Viper's attacks deal an additional instance of physical damage per missing health percentage of the target hero.

Viper Strike

Viper slows the targeted enemy unit's movement and attack speed while also disabling their passives and dealing poison damage over time. The slowing effect reduces over the duration of the poison.