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'''Lifesteal''' is a mechanic which heals a player by a portion of the damage they deal to an opponent. There are two main types of lifesteal, each with an associated [[stats|stat]]: {{plink|Bullet Lifesteal|pic=AttributeIconBulletLifesteal}}, which returns a portion of the [[Bullet Damage|bullet damage]] dealt, and {{plink|Spirit Lifesteal|pic=AttributeIconSpiritLifesteal}}, which returns a portion of the [[Spirit Damage|spirit damage]] dealt. Bullet and Spirit Lifesteal are calculated independently, but use the same formula.

== Calculation ==
While lifesteal is shown as a percentage (like +20%), different sources of lifesteal do not simply add together. Instead, they stack '''multiplicatively'''. This means that as you gain more sources of lifesteal, each new item is slightly less effective than the last.

To calculate your final lifesteal, you can use the following formula:

<math>\text{Total Lifesteal} = 1 - (1 - L_1) \times (1 - L_2) \times (1 - L_3) \dots</math>

(Where <math>L</math> is the lifesteal value of each source expressed as a decimal, e.g., 0.20 for 20%).

=== Example ===
If you have 22% Bullet Lifesteal from {{item|Fury Trance}} and 30% Bullet Lifesteal from {{item|Leech}}, your lifesteal is calculated as follows:
# Convert the percentages to decimals: '''0.22''' and '''0.30'''.
# Subtract each from 1: (1 - 0.22) = '''0.78''' and (1 - 0.30) = '''0.70'''.
# Multiply those results together: 0.78 × 0.70 = '''0.546'''.
# Subtract that result from 1: 1 - 0.546 = '''0.454'''.
# Your final Bullet Lifesteal is '''45.4%'''.

Note: The in-game user interface is inconsistent with rounding, so it may display as 45% or 46%.

=== Lifesteal vs. Creeps ===
Lifesteal against creeps (non-hero units) is reduced compared to heroes:
* '''Bullet Lifesteal vs. creeps:''' 60% effectiveness (e.g., 10% lifesteal becomes 6%).
* '''Spirit Lifesteal vs. creeps:''' 40% effectiveness (e.g., 10% lifesteal becomes 4%).

== Bullet Lifesteal ==
Bullet Lifesteal returns a percentage of all outgoing [[Bullet Damage|bullet damage]] to the player as health.

{{HeroIcon|Graves}} has starting {{#invoke:HeroData|get_hero_var|hero_necro|BulletLifesteal|3}}% Bullet Lifesteal.

=== Sources ===
{{Item stat table|Bullet Lifesteal}}

== Spirit Lifesteal ==
Spirit Lifesteal returns a percentage of all outgoing [[Spirit Damage|spirit damage]] to the player as health.

=== Sources ===
{{Item stat table|Spirit Lifesteal}}

=== Soul Shredder Bullets ===
The debuff applied to opponents by {{item|Spirit Shredder Bullets}} behaves differently from all other lifesteal items. It does not affect the user's Spirit Lifesteal stat, nor is it factored into the multiplicative formula; instead, it '''adds''' a flat +8% spirit lifesteal against an affected target while the debuff is active. 

For example, if a player has Spirit Lifesteal (+16%) and {{item|Leech}} (+30%), their base spirit lifesteal is 41.2%. Against a target affected by Soul Shredder Bullets, it would be:

<math>\text{Total Lifesteal} = [1 - (1 - 0.16) \times (1 - 0.30)] + 0.08 = 49.2%</math>

== Melee Lifesteal ==
{{main|Melee Lifesteal|Lifestrike}}

Melee Lifesteal is not a stat. The item {{item|Melee Lifesteal}} and its upgrade {{item|Lifestrike}} both provide a passive ability which heals the user by a percentage of their [[Melee Damage|melee damage]] dealt, but they behave differently from Bullet and Spirit Lifesteal. 

These abilities activate for one melee attack, then go on cooldown for several seconds, during which no further health can be regained from melee attacks. In contrast, Bullet and Spirit Lifesteal are always active and have no cooldowns. These items also grant a flat healing bonus on activation, and are less effective against non-[[hero|heroes]].

{{Stats}}
[[Category:Stats]]