Lifesteal

Lifesteal allows the attacking unit to gain health when damaging an enemy, which includes any attack modifier with attack damage. The lifesteal ability can be gained via items, passive abilities or the auras of other units.

The amount of health a unit gains from lifesteal is calculated by a percentage of the actual damage done to the attacked unit, but still heals for overkill damage, so if an attack's damage exceeded the target's current health and killed it, the heal is based on damage it would have taken if it would not have died.

All sources of lifesteal stack additively with each other.

Interactions with other abilities

 * Lifesteal is calculated after critical strikes, which means that lifesteal heals more on attacks that crit.
 * Illusions do not benefit from lifesteal. However, the particle effects of lifesteal do appear on them. This is to make lifesteal not instantly give away that they are illusions.
 * Secondary targets of instant attacks can be lifestealed off as long as the instant attack is able to carry attack modifiers.
 * If an attack modifier directly adds the damage it deals to the attack damage (like bashes), its damage can lifesteal:

Spell Lifesteal
Spell lifesteal allows the hero to heal from spell damage they deal. Just like attack damage lifesteal, spell lifesteal is calculated by a percentage of the actual damage done to units. This means it does not heal for overkill damage dealt to a unit, so if a spell's damage exceeded the target's current health and killed it, the heal is based on the target's remaining health.

Pseudo-Lifesteal
Some lifesteal abilities work differently from regular lifesteal. Their mechanics are unique to the spell they are provided by.