Death Watcher

Death Watchers can be found in The Arcatraz.

Attacks and Abilities
Casts:
 * Mark of Death (casts anyone in LoS. When the time runs out of the debuff and the demon is still alive, all targets take 5000-5500 shadow damage)
 * Drain Life (Drains the target of 300 health over 5 sec. Heals the caster for 5000 health over 5 sec. Considered a magic effect and can be dispelled from the tank.)

The demon must be killed before the time runs out on the debuff, else anyone with the debuff will lose 5000-5500 health. The demon has 48k hp.

Note: The Mark of Death Debuff can be removed with a Rogue's Cloak of Shadows.

Heroic

When fighting the Death Watchers on Heroic, it's important that only the tank gets the debuff as its damage is now 10-11k. The debuff is applied when the mob's health is reduced to 50%. You can position the tank so that they tank the Death Watcher inside an archway whilst staying in LOS of healers. Thus Healers are out of LOS of the Death Watcher but in LOS of the tank at all times. DPS classes can be in LOS of the Death Watchers just prior to 50% at which point they need to run out of LOS to prevent the debuff from being applied to them. Once the tank has the debuff, DPS can run back in and finish off the mob.