Consumes 3 Shadow Orbs to deal (300% of Spell power) Shadow damage and then an additional 100% of the initial damage over 6 sec. Heals the caster for 100% of damage done.
"When the shadows are through with you, there will be nothing left, not even your bones." —Deacon Markus Hallow[1]
Devouring Plague is a Shadowpriest ability, learned at level 21. It is an instant cast Shadow-based spell that consumes 3 [Shadow Orbs] to deal instant damage and apply a damage over time debuff, which heals the caster each time it deals damage.
Both of Devouring Plague's damage components are capable of critting. However, its healing component is not capable of critting.
Devouring Plague's damage and healing are directly increased by the priest's haste. Using haste effects shortly before Devouring Plague can therefore serve to increase not only DPS, but also the healing generated.
Devouring Plague is a direct alternative to [Psychic Horror] as a use for Shadow Orbs. Psychic Horror offers more damage mitigation and crowd control benefits with its horrify effect, while Devouring Plague offers substantial damage and self-healing. Devouring Plague's short duration and lack of cooldown also makes it available more frequently.
If the cast misses or is evaded by the target, no Shadow Orbs will be consumed, allowing you to try again.
As a disease, Devouring Plague can be dispelled by paladins' [Cleanse] and healing priests' [Cure Disease]. This makes it possible to remove this effect from targets with [Unstable Affliction] without triggering its dispel effect. Holy paladins run the risk of doing so, however, due to [Sacred Cleansing].
As a disease, Devouring Plague cannot be dispelled by the usual magic dispelling effects, preventing most classes from removing it. However, effects like [Divine Shield] and [Ice Block] will still remove it.
Be aware that recasting this on a target already afflicted by your Devouring Plague will overwrite the older debuff, wasting damage and healing, even if the new debuff is weaker.
Patch changes
Patch 6.0.2 (2014-10-14): Now always costs 3 Shadow Orbs, and now heals the priest for 100% of all damage it deals, instead of healing per tick. Now heals for 2% of maximum health per tick (up from 1%).
Patch 5.0.4 (2012-08-28): Changed. Now consumes all Shadow Orbs.
Previously: Afflicts the target with a disease that causes X Shadow damage over 24 sec. 15% of damage caused by the Devouring Plague heals the caster. This spell can only affect one target at a time.
Patch 4.2.0 (2011-06-28): Devouring Plague damage done has been decreased by 12%.
Patch 3.2.0 (2009-08-04): Cooldown removed but may only be inflicted upon a single target.
Patch 3.1.0 (2009-04-14): This spell now has a new icon.
Patch 3.0.3 (2008-11-04): The bonus coefficient has been increased to be on par with other DoT spells. Base damage on ranks 7, 8, and 9 decreased to partially compensate for better scaling.
Patch 3.0.2 (2008-10-14): Devouring Plague made available to all priests.
Patch 1.12.0 (2006-08-22): Will continue to heal the caster after the target is Mind Controlled.
Patch 1.10.0 (2006-03-28): No longer keeps players in combat for its duration.
Patch 1.8.0 (2005-10-10): Will now properly consume the Inner Focus effect when cast.
Patch 1.6.0 (2005-07-12): Health leech effects no longer give you health while you are a ghost.
[Solace and Insanity]
[Shadow Orbs] to deal instant damage and apply a damage over time debuff, which heals the caster each time it deals damage.
[Psychic Horror] as a use for Shadow Orbs. Psychic Horror offers more damage mitigation and crowd control benefits with its horrify effect, while Devouring Plague offers substantial damage and self-healing. Devouring Plague's short duration and lack of cooldown also makes it available more frequently.
[Cleanse] and healing priests' 
