If you refuse to submit your life to Gehrman, you must fight him. What happens when you win depends on whether or not you’ve consumed three Third Umbilical Cords. In the video clip, I have consumed them. Upon Gehrman’s defeat, the Moon Presence descends to take me—but cannot—leading to one last boss fight.
Gehrman should be considered the final boss, and is very worthy of that distinction. He is without a doubt the toughest challenge I faced during this, my first playthrough of Bloodborne. There a few key pieces of advice I can give. When he wields the Burial Blade as a scythe is when he is most dangerous. If you wander too close, he’ll quickly pull you in and unleash a devastating combo. Keep your distance and wait for him to start his charged attack. This is your best chance to stagger him and perform a Visceral Attack. When he switches to his blade and gun, just dodge his attacks while trying to sneak in a few of your own.
Eventually, he’ll enter a kind of meditation state which will allow you to lay into him quite a bit, but be careful. There are two versions of this state, one of which ends in a very damaging explosion. In the video clip you can see the harmless version at 1:50, where he’s simply buffing himself. At 3:20, he’s charging up for the AoE attack. I was able to finish him off before he went critical, but make sure to go in with full health and/or back off early.
Patience and good dodging will go a long way. Oh, one last thing. When he flies up into the air to unleash his shockwave attack, you want to move towards him, not away. May the Good Blood guide your way my friends.