Ebon Plaguebringer

Ebon Plaguebringer is a Death knight talent located in the 6th tier of the Unholy Tree. It causes diseases to apply the Ebon Plague, which increases magic damage in addition to increasing disease damage.

Though this effect is generally useful for synergy with casters in your group, it also improves many of your own abilities including the shadow damage portion of Scourge Strike, and Death Coil (death knight ability). Unlike similar magic damage debuffs, Ebon Plague can be easily spread by Pestilence.