Mal'ganis

Mal'ganis was sent by Tichondrius to corrupt humanity with infected grain. His servant Kel'Thuzad, though he helped in spreading the plague was ultimately loyal to the Lich King. As the plauge spread through the streets of Stratholme, Mal'ganis faced Arthas but lost and fled to Northrend. Once Arthas attained the cursed blade Frostmourne he killed Mal'ganis at his base.