As expected, Selunelia ended up fighting our hero to prevent him from reviving the big bad.
She has 17 attacks, which I think is the highest number in the game, and most of her attacks inflicts a debuff/status effect.
This time around, the amulets are actually useful since the background's color will change, letting you know which element she's going to use.
Light and Dark are the most damaging elements, but earth is also dangerous due to the pesky poison (10% HP per turn, I think).
She doesn't have her fighting mode yet, but once her HP drops low enough, she will resort to using charm magic. It's pretty lewd, which I can always appreciate.
Most of her charm spells don't deal any damage, because she's mostly focusing on draining MP and levels. It's basically a DPS race. If you don't beat her fast enough, then she'll drain you all the way down to level one.
Most of her charm spells increase the ecstasy gauge, and if she uses a lewd attack and fills the gauge, then she will finish off our hero in her finish animation. However, unlike how it usually goes, the fight doesn't end there. She'll just drain even more levels. Nice.
She's pretty tough, but she's not too hard if you know what you're doing.
Just keep damaging her while keeping your ecstasy gauge low and you should be fine. If it gets high, then she could charm you with lust charm and you'll lose about 60 MP per turn. You'll probably lose if that happens. Unless you cheat and spam items like a real hero.
It seems that we'll be going to the monster lord's castle after Selunelia's fighting mode is done. No clue if we'll meet/fight anyone there, though.