Lifesteal

Lifesteal is usually referred to in a Basic Damage sense, but there is a Gem in Intellect that provides Ability Lifesteal. In both cases, the healing is based on the actual damage dealt after Defense Rating is factored. It is not capped by the target’s actual remaining Health. Meaning if you Critically Hit a Minion for 500 damage but the Minion had only 40 Health, you will still heal for the % of that 500 damage.

A thing to note is Lifesteal does apply to abilities that deal Basic Damage such as Serath’s Heaven’s Fury.

Spell Lifesteal also exists, and it works exactly the same as regular Lifesteal, except it is based on your ability damage.

Formula

((Lifesteal Rating/ 100) * Damage) as base healing power

Mechanics
Hero	Abilities ● Affinities (Death/Chaos/Growth/Knowledge/Order) ● Aura ● Basic and Ability Armor ● Attributes (Agility/Vitality/Intellect) ● Cards ● Cooldown ● Cooldown Reduction ● Experience ● Jump ● Gems ● Gold ● Health ● Mana ● Movement Speed (Movement Speed Penalty)
Attack	Armor Penetration ● Attack Speed ● Basic Attack ● Basic Attack Time ● Basic Attack Modifiers ● Damage over time ● Lifesteal ● Power
Status Effects, Buffs and Debuffs	Blind ● Crowd Control ● Immunity ● Metamorphosis ● Rewind ● Shadow Plane ● Shield ● Silence ● Slow ● Stasis
World	Agora ● Minimap ● Backdoor Protection ● Core ● Fog Walls ● Fountain ● Jump Pad ● Minions ● Neutral Monsters (Aqua Camp/Black Camp/Fangtooth/Gold Camp/Green Camp/Prime Helix Guardian/River Camp/White Camp) ● Tower ● Wards
Gameplay	Ganking ● Harassment ● Initiating ● Jungling ● Kill ● Lane ● Pushing ● Respawn ● Traits
Legacy	Red Camp ● Blue Camp ● Altar ● Amber Link ● Harvester (Harvester Keys) ● Raptors ● Shadow Pads ● Travel Mode