Kostaltyn
The Supreme Patriarch of The Great Orthodoxy, Kostaltyn is an original Legendary Lord for Kislev in Total War: Warhammer 3. Being the child between Creative Assembly and Andy Hall.
Since Game 3 is currently still in development and CA is still holding Kislev and Kostaltyn very close to their chest, we don't know that much about him. What we do know is that he is the current head of The Great Orthodoxy, the union of the major religions of Kislev. He also apparently does NOT get along with Tzarina Katarin, which makes sense, given the tension between the all male religious order of Kislev and the all female Ice Witches. If you couldn't tell, he is heavily inspired by Rasputin, which yes, is memed within the community.
Similar to the other Total Warhammer OC, Cylostra Direfin, the reception of this man was... mixed. Some say that he is an excellent addition to help flesh out the rather small collection of named characters Kislev has and has an awesome design. Other say that he was completely unnecessary and that he stole Tzar Boris's spot as the second Kislev Legendary Lord. No, this disagreement probably won't end for a very long time.