I am still proud that I could defeat the boss in normal mode and watch the final ending on it.You might have already figured it out, but that's because you're meant to lose to the final boss your first run through, though it's still possible to negate unavoidable Obey damage with the Mistress card. Have to play hard mode to get the real ending, but that seems to be unfeasible before you've ground enough talent points to unlock the extra permanent mana point.