Leech

Leech recovers an amount of life, mana or energy shield over time, relative to the damage inflicted on an enemy. Leech cares about the damage taken by the enemy, not the amount of life removed.

Mechanics
All leech mechanics act the same way for life, mana and energy shield. Examples in this article will use life, but if the character has equal statistics for a different resource (mana or energy shield), they will apply in the same way.

Whenever a character with some source of leech hits a monster a leech instance is created. A life leech instance has the following properties by default: Multiple leech instance stacks and apply to the character simultaneously which will lead to the total life leech rate increasing. There is no limit in number of active leech instances but the total sum of leech rate is instead limited to % of maximum life per second. The extra healing over that cap will be ignored. Reaching the max leech rate is quickly achieved when using an area of effect skill, a single hit that struck 10 enemies will result in 10 separate leech instances.
 * Each life leech instance is independent.
 * Recovers the character's life for the Damage Dealt * up to % of maximum life.
 * Recovers at a rate of % of maximum life per second.
 * Recovers until the instance expires or the character is at full life. Therefore at full life all instances are removed.

Leech grants recovery to the entity that hit the target. If a minion or totem with leech hits another monster the leech will grant recovery to that minion or totem only, not the character. Leech on a trap or mine has no effect, as the source of the hit has no life to recover.

Modifiers
Leech can be modified significantly through passives, support gems, and equipment. Beyond just adding various sources of leech, modifiers such as or  can change how leech is applied to a character.


 * increases the default % of the character's maximum life pool leeched per hit/instance to % of the character's maximum life pool leeched per hit/instance.


 * increases the default % of maximum life that can be recovered as life per second from a single instance to % of maximum life recovered as life per second from a single instance.


 * increases the default % of maximum life that can be recovered per second from all instances combined to % of maximum life that can be recovered per second from all instances combined.

There are a few notable ways to affect leech:
 * The modifier for maps slows life and mana leech recovery rate by 50%.
 * For life leech by a skill supported by the gem.
 * and the Tukohama, War's Herald passive, which allow other entities to leech life to you.
 * Brutal Fervour or allows leech instances to continue even if the character has reached full life.
 * Players can become immune to being leeched from items such as
 * Items such as prevents the user from leeching.

Leech duration
The leech recovery duration is how long in seconds a leech instance will last, based on damage dealt and character's Leech modifiers.

By default a maximum of an instance is % of character's maximum Life, and maximum Rate is % of character's maximum Life per second, resulting in a maximum seconds duration of a single Leech instance.

Combined Recovery Rate
The total leech recovery rate (accounting for all instances of leech) can be calculated by

where  can also be the character's maximum mana or energy shield.

This combined rate is subject to the total leech rate cap, which is by default % of the character's maximum health. This maximum is increased by modifiers.

As such, each character only requires a certain number of leech instances before they will be recovering at their maximum rate. This maximum can be found with the below formula:

For a default character, this is instances, but any increases or decreases from  or   will change this number. If a character has too many leech instances, the extra healing will be ignored.

Types of leech
There are several types of leech that specialize on certain types of skills. Some leech types only work for attacks, others only works with elemental damage or all sources of physical damage. If there is specialization it will be defined in the modifier.

Generally the leech modifiers follow this template:

Where can be:

can be:

and can be:

Note that if, or  are not specified it means that it applies to all those types.

A couple of examples:
 * has the mod implying it works for all types of skills that hit a target.
 * has the mod, specifying it applies to attacks. All types of damage from the attack will be counted, but not Spells.
 * The notable passive Lust for Carnage grants the mod specifying it applies to Physical Attacks. All types of weapons can make use of this notable, however not Spells.

Other items

 * Elder amulets can have.
 * Elder amulets can have.
 * Elder amulets can have.
 * Shaper amulets can have.
 * Shaper amulets can have.
 * Shaper boots can have.
 * Shaper gloves can have.
 * grants to weapons or quivers.
 * grants to weapons or quivers.
 * grants to amulets.

Passive skills
There are passive skills that grant passive leech or bonuses to leech.

Attack Damage Leeched as Life
These passive skills grant passive life leech when dealing any damage with a weapon.

Increased Life Leeched per second
These passive skills increase the rate of life gained while leeching.

Increase to Maximum Life Leech rate
These passive skills increase the maximum life leech rate.

Minion Life Leech
These passive skills grant life leech for minions.

Keystones
These keystone passives change the way Life Leech works, but do not directly enhance Life Leech. These effects do not apply to Mana Leech.

Attack Damage Leeched as Mana
These passive skills grant passive mana leech when dealing any damage with a weapon.

Increased Mana Leeched per second
These passive skills increase the rate of mana gained while leeching.

Increase to Maximum Mana Leech rate
These passive skills increase the maximum mana leech rate.

Version history

 * Added Energy Shield Leech. This is functionally similar to Life Leech, except it leeches to your Energy Shield and is limited by your maximum Energy Shield Leech Rate. Several passive skill clusters have been added to support this new form of leech.
 * Added a cap on the amount of any resource you can leech from any individual instance of leech. By default, that cap is 10% of that resource's maximum. In other words, a character with 4000 life will, by default, be able to leech a maximum of 400 life from a single hit.


 * Multiple leech effects now stack. A single hit against multiple targets grants multiple effects, as do multiple hits against a single target.
 * The speed at which you leech has been substantially reduced for both life and mana, with less of a reduction to mana leech rate, bringing it in-line with life leech rate. These now default to 2% of maximum life per second. It can be increased.
 * A maximum leech rate caps the rate at which you can leech. It's set to 20% of maximum life or mana per second.
 * Methods of improving leech, leech rate and increasing your maximum leech rate have been added to new clusters in the passive skill tree, primarily in the regions between the Marauder, Duelist and Ranger.
 * Some of the already existing clusters in this region that specialized in specific weapon types have also had leech elements added to them.
 * All existing values of leech have been substantially reduced, including values on existing items.
 * Some things such as Support Gems and Warlord's Mark have had their values brought in line with the other leech changes.
 * Previously, we had modifiers for "increased (or reduced) Life/Mana Leech rate". These did two things: They increased the amount of Life/Mana you're gaining per second for each leech effect and they reduced the duration of each leech effect, such that the total life/mana gained over the duration remained the same. All such modifiers have now been changed to "increased (or reduced) Life/Mana Leeched per second". This still increases the value of Life/Mana you're gaining per second for each leech effect, exactly as it did before. It no longer affects duration of the leech effects, meaning you'll gain more total life/mana from each one as a result.
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