Brawler Birka can be found in the Worg Pens within the Shattered Sanctum, encouraging One and Three to throw stones at an imprisoned cave bear. With one exception, Birka is doomed to be killed by the bear during a cutscene.
It is possible to convince Birka to open the cell doors using Illithid Persuasion, but the bear will initiate combat once freed. The only possible way for Birka to potentially survive is to join the goblins in killing the bear. It is not possible to lure Birka away from the pen through committing crimes, vandalism, enchantment, or methods such as Perform or Minor Illusion.
If the party initiate combat from a distance without triggering the cutscene, Birka will still be killed in a future cutscene by the cave bear once combat reaches the bear's turn.