The Mark of Kathra'natir is a powerful corrupting curse. Once the curse is cast, the subject becomes the host of the dreadlord Kathra'natir.
Vendellin Soulfire cast this spell on Valeera Sanguinar during her journey to Stormwind with Varian Wrynn, Broll Bearmantle and Thargas Anvilmar.
Aegwynn helped her deal with the curse and Meryl Winterstorm later challenged the dreadlord to possess him instead it.[1]