Cast when Damage Taken Support

Cast when Damage Taken is a support gem. It causes a linked spell to trigger when the player takes a certain amount of damage.

Skill functions and interactions
Trigger gem: Like all trigger gems, Cast when Damage Taken only "casts" spells. Attack gems such as Double Strike are not considered spells. Multiple spells can be linked to a single trigger gem, and will all be triggered if so. Multiple copies of Cast when Damage Taken will also function independently.

Damage counter and cooldown: Each linked spell gains an internal damage counter that tracks the total accumulated damage taken from hits, though not from damage over time or the Blood Magic passive (e.g. you cannot use to trigger Cast when Damage Taken). All damage counters will be reset to 0 upon entering a new area. When a linked spell is cast, it is put on cooldown for 250 ms and will not track damage during that time.

Multiple copies of the same gem share cooldowns, meaning that if two copies of the same spell are triggered within 250 ms of each other, the first will trigger and the second will fail to do so as it is on cooldown. This mostly prevents using multiple copies of the same spell with Cast when Damage Taken, though the use of Cast when Damage Taken gems of different levels can avoid cooldown overlap in some circumstances due to the differing amounts of damage required to trigger the spells.

The Cast when Damage Taken gem itself does not have its own counter or cooldown.

Maximum level of supported skills: Cast when Damage Taken cannot support skills with a higher player level requirement than that of Cast when Damage Taken itself. Note that this restriction only applies to active skills; any level of other support gems may be used.

Trigger order: Trigger gems and their linked skills are cast in a certain order that depends both on which item it is equipped on and which socket the skills are in. If there are trigger gems in each equipped item, the order of operation will be:


 * Main hand ⇒ Amulet ⇒ Helm ⇒ Off hand ⇒ Body armour ⇒ Gloves ⇒ Boots

The linked sockets also follow a specific order, as follows:

Damage effectiveness: The damage effectiveness increases with level, but so does the damage taken per cast; overall, the amount of damage that needs to be taken per damage effectiveness goes up at higher gem levels. The optimum is a level 2 gem, which requires 1442 damage taken per 100% damage effectiveness. In comparison, a level 20 gem requires 3057 damage taken per 100% damage effectiveness.

This does not, however, take into account the increase in damage from being able to use a higher level gem; for instance, a level 4 gem deals an average of 91.5 damage, while a level 20 gem deals an average of 475. On a strict damage-in-per-damage-out basis, Cast when Damage Taken roughly triples in power between level 1 and level 20, depending on the skill used. Any flat added damage will affect this ratio—the more damage added, the less effective it is to level up the Cast when Damage Taken gem.

Targeting: Targeted spells will cast towards the enemy that caused the last damage. Reflected damage is considered to come from the enemy originally damaged. If the damage was self-caused, it will target a random enemy (if there are no enemies, it will be cast at the player, if it is a projectile, it will be fired in a random direction).

Totems: Cast when Damage Taken can't be used with totems.

Related unique items
The following unique items are related to Cast when Damage Taken Support:

Strategy
Due to the large amount of damage taken needed per damage effectiveness and the rapid scaling of damage taken required per level, it is advisable to use spells for purposes other than damage that do not depend heavily on the active skill level. Possible choices include:

Offensive:
 * to proc Elemental Overload for slow hitting/no hitting builds (e.g. DOT).
 * Can be linked to for even more consistent crit.
 * Rapid-fire duration skills such as or  for applying Elemental Overload and Elemental Equilibrium.
 * for applying Exposure
 * for applying Cold Exposure and reducing enemies' Life/Energy Shield regen
 * for Frenzy Charge generation
 * for Unnerve
 * Offensive curses such as, , , , , , etc.
 * Offensive golems such as, ,

Defensive:
 * Guard skills such as, , ,
 * Only one guard skill should be used in all CWDT setups, as they share their cooldown
 * can be used to increase the duration
 * for increased block chance.
 * for Elusive and Phasing.
 * for increased movement speed, reduced visibility and Phasing
 * Useful for builds that often run past packs such as minion or DOT builds
 * Make sure Phase Run is the last skill to be triggered in all CWDT setups
 * to block enemies.
 * , or  to chill enemies.
 * Can be linked with for increased chill effect
 * to create Consecrated Ground
 * ,, or for passive corpse disposal and minion buffing
 * to escape melee range (could backfire).
 * Defensive curses such as ,
 * Defensive golems such as,.
 * Can be linked with

Other:
 * for builds that die often.
 * is often used in AFK boss kill attempts such as Uber Elder or Sirus.

Some supports also potentially combine well, especially with a persistent rapid-firing skill such as :
 * Passive IIR culling via, , and a skill that causes many hits.
 * (As of Version 1.2.2 CWDT will only trigger Ball Lightning in this example, Ball Lightning will then only trigger Hextouch if the supported curse is above the CWDT level threshold.)
 * Passive IIR culling via, , and a skill that causes many hits.
 * (As of Version 1.2.2 CWDT will only trigger Ball Lightning in this example, Ball Lightning will then only trigger Hextouch if the supported curse is above the CWDT level threshold.)

Quick reference chart of commonly used spell gems and their maximum allowed level to be supported by each level of CWDT:

Cats when Damage Taken


Cats when Damage Taken was a trigger gem available only on April 1, 2015 as an April Fool's joke. Like Cast when Damage Taken, it caused a linked spell to activate when the player accumulated damage taken, but besides casting the spell, it also summoned black cats. Other properties were identical to the Cast when Damage Taken skill.

Version history

 * (Not documented in patch note) the Divergent alternative gem quality has changed to


 * Now has alternative gem quality:
 * Anomalous: (per 1% quality)
 * Divergent:  (per 1% quality)


 * Enduring Cry is now a Warcry instead of a spell, therefore it can't be cast anymore.


 * Fixed a bug with the trigger gems that cause spells to automatically cats on various conditions.


 * Spells triggered by Cast on Damage Taken have had their damage reduced by 25%.


 * Trigger gems are now classified as Trigger.


 * Gems may now only be supported by a single trigger gem, gems supported by multiple trigger gems will be disabled.


 * The level requirement of gems augmented by Cast on Damage Taken may not exceed the level requirement of the Cast on Damage Taken gem.


 * Cooldown of 250ms added.


 * Cast when Damage Taken has been added to the game.
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