[x] Use the explosions as cover. Hop back into a non-burning part of the field and cast a Holy Ward, wrapping bible-page armor around your torso and limbs. Pray for the ward to spare followers of Christ and burn non-believers.
-[X] Then break the Old Hunter's Bone (insert appropriate quip considering it's probably Gherman's tibia) and go back in. Take out his legs, get him on the ground.
-[X] Store the Amygdalan arm in the clutch of the Amygdalan spring-loaded fist, then have that grip the Amygdalan club. Hit him with the arm of a false god wielding the arm of a false god wielding a club made out of a false god. He'll be too busy being impressed to dodge.
-[x] Taunt Gehrman for his hypocrisy. Point out that he's got a s**t-ton more reasons than you to lay down his weapons and accept his death...and yet he refuses. Because he too has a duty to fulfill...and because this fight is f**king fun!