I want to talk about the cast when damage taken in Path of Exile. Cast one damage taken, commonly abbreviated as cwdt, is one of the trigger skills in the game. It is a great way to automate some defense and utility into your build. When damage taken becomes available at level 38, it can be linked with active spell gems. Those spell gems can be linked with support gems in order to increase their effectiveness.
The cast The damage taken gem will automatically cast spells that are linked to it upon taking damage.
The amount of damage taken that is needed to trigger these spells is 528 at level 1 and increases as you level up the gem. The gem’s player level requirement also increases as the gem levels up. Any active spell gems that are linked need to be of the same or lower player level requirement in order to cast automatically, so you will have to watch out for over leveling any gem that you wish to remain part of the cast when damage taken setup.
However, any support gems linked to these spells.
They can be leveled all the way up and don’t have to worry about this requirement. Keep in mind that these skills will not be able to actively be used by the player and cast when damage taken cannot support skills such as totems, traps, minds, veil skills, channeling skills, or any skills that reserve mana. The most common use for this setup is linking a guard skill. Such as steel skin immortal call or molten shell. Alongside the increased duration support gem, which will give you a bit more defense as you take damage.
However, it can also be quite useful to link cast one damage taken to your curse skills and other skills.
Such as those that can apply elemental exposure. For instance, if you are dealing mainly fire or lightning damage, it might help to link wave of conviction. It needs in order to reduce the fire or lightning resistance of enemies in front of you when you take enough damage to trigger the spell.
For fire builds, you could even add in the combustion support gem to the setup. It needs to further lower the fire resistance of the enemies hit by that wave of conviction. I personally keep my cast one damage taken gem somewhere between level 3 and level 8 for most of my builds so that it procs at regular intervals, though it is also worth noting that any spells in this setup will still have all cooldowns associated with them cast when damage taken is not normally used for damage-dealing abilities.