Leech

Leech (or lifesteal/manasteal) effects take away life or other resource like mana from a target and giving it to the caster, or transform a % of the damage dealt to health or mana/resource.

The resource received does not have to correspond with the damage dealt, and in many cases a character could get a part of the health back, or a multiplication of the damage dealt.

Leech/lifesteal is not the same as drain or bleed, but the effects are similar, and can sometimes be combined.

Leech in Diablo III

Leech was quite overpowered in Diablo II, was widely available on all types of weapons and also on many unique and set helms, armors, gloves, belts, and more. This contributed to that game's erratic difficulty curve. Thanks to the ready availability of leech (and to a much lesser extent potions), all well-equipped melee characters in Diablo II could keep their health (and mana) constantly topped off. As a result, monsters needed to be able to kill a character almost instantly in order to pose any real threat.

The Diablo III team has learned from this issue, and besides largely removing potions from the game (and adding in health orbs, they've greatly reduced the frequency of leech. It will be found very rarely (if at all) on equipment, and comes only from a few skills and traits.

These changes make it much harder for characters to heal and to stay at full health, which makes monsters dangerous again, even if they can't kill a character in one shot.

Leech Sources in Diablo III

No item stats are yet known to provide leech. A few skills and traits do, in limited fashion:

• Revenge -- A Barbarian skill that boosts damage and grants a % of life steal.
• Drain Power -- A Wizard trait that transfers a % of damage done with spell damage to health and Arcane Power.

Formerly:

• Bloodthirst -- A Barbarian skill that provided life leech for a limited duration. Removed from the game during development.