The Kravenrook is the boss found at the end of the dungeon for the quest If It Bleeds.
It is first encountered halfway through the dungeon where you must sneak past it and burn its effigy, then encountered again in a fight at the end.
For each effigy burnt during the quest it will lose a percentage of HP, making the fight notably easier.
It can also be stunned by making it jump into the pillars found around the room.
After being defeated, you can loot the Kravenrook head off the corpse which can be used for additional dialog in Shipwrecked Anubites.