I'm not sure what is happening under the hood but I have been grinding the tomb with the Lich in it (haven't tried to fight him yet ) and when I do a 12-hour rest the game regularly crashes as long as I have the wolf still active. On the rare occasions that it doesn't crash (or not immediately) it will still chug along pretty slowly as the wolf is despawned (and there appears to be some blue text floating to heaven but it moves so quickly I can't read it).