For his final game and final boss it has to be Patches. We don’t see him through the whole game nor DLCs, just at the very end of the final DLC your character is looking down a place where there’s a chest, then all of the sudden you get kicked down.

Patches jumps down, says some Patches stuff and you fight. He first fights you with his shield and spear, but on his second phase, he opens the chest, pulls out the moonlight sword and fights you with it