A boss created by a demon god

In the Tower of Truth, on the seventh level.

A Frigid Cliff.

"Whew—" The biting cold wind, sharp as a knife, whipped across the face, bringing waves of pain.

Just before Mike entered the seventh level, several figures shrouded in black robes stood at the summit of the Frigid Cliff, facing each other.

"We shouldn't be meeting like this; it's too dangerous," one of them spoke, their voice clearly altered to sound like a chorus of dozens, including men, women, the elderly, and children, creating a cacophony.

Everyone present was at least a Battle Chief, and under normal circumstances, they wouldn't bother with such a low-level floor. 

Moreover, the Tower of Truth was guarded by [Apollo]. Attempting any mischief under his watch was akin to seeking death!

The strongest among them slowly began, "That one has been in seclusion since yesterday."