hi guys.
i just wanna know 1 thing.
in the nameless' tower, 3th floor, there's a door (the first you can find, just in front of the ladders, coming from 2th floor), that i cant open yet, because it says a sentence as :"the likes of you cant defeat it..."
on the 10th floor, there's a monument, it says that the last door, (sud-east side), can open only if i've challenge the deaper element.
so i've thougth that it can be connected with the door of the 3th floor.
so my question is: how can i open that door? Is there a gilda's quest that allowed me to challange it?
PS: in the game i've already discovered elfort and hokebai, and i reached that strange place where the goddess is, but i haven't still defeated her yet.
thank you all for help!

do anyone can help me??