Sub-Warden Ghula's Room.

[OldPortOutcast]

Without spoiling anything of the encounter itself, the two 'Special Loot' chests in the back can be accidentally destroyed by any area of effect spells.

This prevents a group and any subsequent groups for reaping the best of the additional rewards for defeating the tough optional part of the Tower of Mercy.  The loot does not appear in bags on the ground when the container is destroyed, its just gone.