Blight is the term for the physical corruption of the land by the presence of the Lich King's undead plague. The plague affects all it touches, sterilizing the land, warping its natural inhabitants into bloodthirsty mutants, and twisting the local flora into disgusting mockeries of proper plants. The Eastern Plaguelands (most specifically Plaguewood) and the Dead Scar that runs through Quel'Thalas are perhaps the most startling examples of the long term effects of Blight.