is it the one where you get all four boss buffs duing the fight to beat it? I beat that one
there are
two "final bosses", and they
both have a mechanic like that, so no. when you're at the screen before fighting the red/green/yellow/blue mini-bosses, don't go right. you can instead walk "forward" towards the camera, and get the choice of fighting white/black mini-bosses. they're pretty tough (but were just as trivial as the final boss with a succubus build imo). 20 floors after defeating the 2nd one, you'll be given the option to face the secret final boss. technically, you can face it as soon as floor 60. also, obviously need a newer version than the OP one.
Tips: Save Curiosity's Veil (which I got SPECIFICALLY for this fight) for the same turn you activate Aitros's Protection (special boss battle card), even if you can activate it sooner, since it'll compound the defense bonus the latter gives. Requires getting both of them in your hand at the same time and the right time, but part 2 hits like a truck and you need as much def as you can get.
I think it might actually be easier to deliberately not activate part 2. its defenses fall, but its attacks increase, and it still has a massive HP pool (dynamic to floor count; over 1000 when I faced it).
It was able to one/two-shot me at 10def & 80hp/rp. After grinding a fair bit (see below) I was able to do it with just a little bit of my heart in the cards. 100rp was
one enough rp to not get one-shotted into an orgasm (and probably losing). Like the normal final boss, it required two golden kicks to finish (maybe 3 if you don't activate part 2). But unlike the normal final boss, it took a lot more than 3 turns to get there.
Here's the deck/stats I had. Relief is mandatory. Natal Pray has a limit (I THINK it's 3 times per turn). Refresh is amazing. probably should've had 4 refresh & 2 natal. other than that it's pretty much perfect. Zero room for waste.