Date & Time: 26/12/2021
Frequency: Always
World name: Omega
Monster name: Omega, Fatebreaker, Chaos
Class/Level: Dark Knight/Warrior

Steps:
1. Enter the duty Eden's Promise: Anamorphosis, Alphascape V3.0 (Savage) or Alphascape V1.0 (Savage) as a Dark Knight or Warrior
2. Get to low HP before a damage over time effect is applied - in Anamorphosis it's the third attack (lightning imbued Bound of Faith, used only half the time), in Alphascape V3.0 (Savage), it's the second attack (Mustard Bomb), in Alphascape V1.0 (Savage) wait until Chaos applies the first elemental field and then step into it.
3. Activate Living Dead or Holmgang before the attack connects.
4. The damage over time effect will bypass the death immunity and kill you.

Tested Hallowed Ground and Superbolide as well, those completely nullify the damage from those damage over time effects which makes us believe that this is an unintended bug.