if i remember correctly i think the lost boss i fought was dhoulmagus and he makes 2 clones or something. it was almost like an mmo where you have to go back to town anytime you want to heal.
I hate to tell you this, but that fight is actually the PRE-FIGHT... it's his first/easier form. After you beat his clones, you have to fight him as a wolf/eagle thing, which is much harder. HOWEVER, if you lose, you simply go back to the last church you saved at, and when you return, you don't have to fight his first form again.