Defeat Diran D`Tradis 0/1 (Neriak - Fourth Gate)
Kill Diran, it will summon adds at 76, 31 and 6%, it will also hp lock until they are killed
If you wipe on this mob, his HP will reset to 100%, but you won't need to kill the spawned adds you've already killed.
I wiped at 31% when his second add spawned. Came back to find named with his invulnerability shield and the add up. Killed the add, shield disappeared, beat him down to 6% to get the final add to spawn.