Unhealable Damage - The affected target suffers damage that lowers their Max Health. The Unhealable Damage cumulatively reduces the Max Health to a minimum of 1 if the target does not die beforehand. If the damage is greater than the current health the target dies immedeatly. Since the Max Health and not the current health is affected, the effect is not immediately noticeable because the fill level of the health bar remains at 100% or even increases if it is below 100%. Max Health is reset to the original value when the room is exited.
Type: effect - Category: Health, Damage
See also: | 
Heal | 
Health Loss | 
Lifesteal | 
Max HP Boost | 
Repair | 
Resurrection | 
Unhealable Damage
Unhealable Damage is an effect that reduces the target's Max Health by the amount of damage taken.
Please note: If the target has full health, it may appear that it will not suffer any damage. This is a misunderstanding, since the health bar always shows the percentage of Current Health to Max Health. In this case, it is still 100% but damage is taken in the amount of the number shown.
Example
An opponent has 5000 Max Health. The health bar shows 100% because he has 5000 of 5000 health points.
If he now suffers 2000 Unhealable Damage then Max Health is reduced to 3000 and Current Health is reduced to 3000 as well. The health bar still shows 100% because the opponent still has 3000 of 3000 health points. However, he can now take much less damage and it's impossible to restore Current Health above 3000 points. If the next hit deals 1500 damage then the health bar will be at 50%.
Multiple Unhealable Damage adds up and can reduce target's Max Health to 1 health point.
The Max Health is reset after leaving the current room of the dungeon, so it is not permanent in PvE dungeon runs.
Heroes
The following heroes have or can inflict/apply Unhealable Damage:
Doom Blade (Special Attack): Melee Dark attack on all enemies that deals unhealable damage.
Bog Blessing (Special Attack): Ranged Nature attack on all enemies, healing all allies for a percentage of damage dealt. Lowers SKL, Max Health, and applies Swamped to all enemies hit. Starts Powered.
Purple Rain of Sorrows (Special Attack): Ranged Physical attack on all enemies that deals unhealable damage.
Immunity
There is no known immunity.