Kas the Betrayer

An excerpt from "The Histories of the Planes" by High Archivist of Ioun Samfrey Smallhand
Kas the Bloody-Handed was the arch-lich Vecna's most trusted general in his never-ending war against the Raven Queen. Vecna's forces were about to lay siege to the Fortress of Memories when the scheming vampire decided to seize the arch-lich's power for himself. Wielding his sword, he struck down his master before the attack could begin. The Rotting Tower fell that day. Vecna's Hand was severed from his body and his Eye cut from his head.
...
For according to rumor, Kas had betrayed Vecna to the Lords of the Abyss. To Lolth, the Spider Queen, went Vecna's heart. It was to Orcus, the Prince of the Undead, that the Book of Vile Darkness went, bound in Vecna's skin. To Baphomet, the Horned King, went a chalice filled with the spilled Blood of Vecna. It was to Yeenoghu, the Beast of Butchery, that the Hand of Vecna went. And lastly, to Dendar, the Night Serpent, went the Eye of Vecna.