Boris Ursus
Boris Ursus (born Boris Bokha) is a former Tzar of Kislev and father of Tzarina Katarin.
As can be clearly seen below, he rides a GODDAMN FUCKING BEAR into battle, 'nuff said. Ok fine, we'll also say that he met this bear for an initiation ritual as a priest into the Cult of Ursun (where he had to go into a forest and tame a bear). The tale goes that he tried wrassling it into submission after meeting it but neither could overpower the other and their mutual blood loss attracted a pack of wolves which tried going for the bear first. Boris defended it and was driven unconscious from his ensuing injury. The bear returned the favor and unwaveringly kept him safe (even from Kislevite help looking for their ruler) until Boris woke up, with the two of them having put down over two dozen wolves together. Thereafter, the bear was ever loyal to him, like an ursine-Deathclaw - a Bearclaw, if you will.