Letho

Letho of Gulet, also known as the Kingslayer, is a Witcher from the School of the Viper and the main antagonist in The Witcher 2: Assassins of Kings. His closest associates are Auckes and Serrit, also Kingslayers and Witchers from the School of the Viper. For reasons which were initially unknown, he enlisted the help of Iorveth and the Scoia'tael to aid him in his plan to kill the kings of the Northern Kingdoms. To back his claim, this man showed Iorveth a head he claims belonged to Demavend, King of Aedirn and Sovereign of the Pontar valley.