Is there a secret final boss in this game?

[Castoth]

Heard online that after you clear both story modes, you fight some 'Darkness' enemy (forget exact name) that has 50 or 60 HP. I don't think they were refering to Amplam Umbra though. Is this just something made up or is it true?

[LollipopLolita]

amplam is the offline boss you meet when you clear both sides

http://www.pso-world.com/sections.php?op=viewarticle&artid=1943