Enter the church and speak with Rhombus, who tells you that Blake has the key to his chains. After finishing the conversation and walking towards the center of the torture chamber, Blake enters. He speaks loudly and carries a big stick. After some dialogue, he starts taking swings at you. He is rather slow, so to avoid direct hits, keep a safe distance while locking on to him and firing. He has an alternative attack, a shock-wave blast from slamming his hammer onto the ground. Jumping while the hammers strikes avoids damage, as does avoiding the puddles of toxins that are all through the chamber.