Kasimir trained with the Thranish assassins for many years and was often sent on missions by the more notable Thranish wizards, such as Darcassen Voss Valarion and Vedansh. He was instructed by an unknown master to assassinate the Empress Kaori and frame Nicholas for the act. The wizard Darevor was to help him by using enchantment magic to force Nicholas to kill her. Mira interrupted the act by killing Darevor, and Kasimir was killed by Nicholas.
Kasimir was a skilled fighter and also enjoyed killing. He had powerful political allies and tended to dismiss the specifics of his various orders as technicalities. He wore studded leather armour and carried multiple knives. He had short dark hair and usually kept his face hidden.