The Cult of the Damned began breeding a plagued dragonflight within Scholomance as another method of spreading the Plague of Undeath. The necromancers of Scholomance, working under Vectus, used black dragon eggs from the Burning Steppes as the basis for their experiments, and hopes to unleash the plagued dragons on the world. However, the Argent Dawn has caught wind of their activities and plans, and is working to destroy the abominable plagued dragons before they can be deployed.
Work on the plagued dragonflight appears to have continued in Northrend, as several Plagued Proto-Drakes can be found throughout Icecrown and the Storm Peaks. Kel'Thuzad once nursed a plague-infected whelp to adulthood, feeding it only the finest liquefied remains.