I yell at everyone to turn on bgm for this dungeon whenever I go in 

Titan EX theme - Under The Weight (Final Fantasy XIV)

the epic music when you fight this giant of boss in this awesome free game one of the 3 theme this boss has

【Phantasy star online 2】 Profound Darkness theme IDOLA The Strange Fruits 完全版

A attempt at a transition between Leviathan's original theme and the new remix.

Not affiliated with Square Enix.
Please buy the OST if you can.