"When the shadows are through with you, there will be nothing left, not even your bones." —Deacon Markus Hallow
Devouring Plague is a Shadowpriest ability, learned at level 12. It is an instant cast Shadow-based spell that consumes 50 Insanity to deal instant damage and apply a strong damage over time debuff, healing the caster each time it deals damage.
Ticks scale with haste and damage dealt can critically strike (healing returned cannot crit).
Devouring Plague is the only baseline ability that costs insanity.
Shadow priests may talent into Searing Nightmare which also costs insanity and competes with Devouring Plague in multi-target scenarios.
Uses the same refresh mechanic as [Mastery: Ignite], where reapplying the effect early will roll all of the previous remaining damage into the newly applied DoT. This means that unlike other DoTs, refreshing Devouring Plague early at any point will never cause a loss of damage.
For a time between patch 9.0.1 and patch 9.0.2, Devouring Plague was learned before [Shadowform]. Since Shadowform is necessary to use Devouring Plague, this made the skill unusable until Shadowform could be learned. Eventually, the levels at which Shadowform and Devouring Plague were learned at were swapped.
Tips and tactics
Devouring Plague is one of the three periodic effects that "applies" [Mastery: Shadow Weaving] to the target. Therefore it is ideal to refresh the effect near its end in order to maximize its uptime, so long as the priest will not cap their insanity doing so.
While in [Voidform], shadow weaving applies its full effect to all targets regardless and players should instead prioritize casting Devouring Plague whenever possible.
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%).
Previous ability: 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 (was 3 minutes), but now 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 instead of just Undead.
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.