People: Azalor Maltheridas, the Omega
He has no equal.
The Omega was finally defeated in CR 466 by the Faithful Faithless, in a demiplane that existed in the space between prime material planes.
The history of the Omega is shrouded in mystery. What little follows is what is known about him to a select few.
During the reign of the Kiltians, two brothers - Lexicon and Azalor Maltheridas - were born. Azalor became a priest of one of the True Gods, while Lexicon - through unknown means - became a Wanderer.
Lexicon saw fit to slay the deities, and this enraged Azalor. What right, thought he, does any have to usurp the natural order of things? What is this power wielded by a mortal, that he can disrupt the very fabric of existence with his being?
And so Azalor sought out a power of his own, and found ancient secrets, deep and terrible. He shattered his being - his body, his mind, his soul - into nine disparate components, and bound them to the three Towers he constructed in the far corners of the world.
There he plans and waits, invincible against those who would thwart him, his grand design stretching across the aeons, waiting for the time when his powers will coalesce and he will become more than even his brother can dream.
He is become the Omega, and with his might he will bring the Wandering Age to an end with unyielding finality.
The Omega is.
Omega is constrained not by your petty rules. His power usurps yours, and there is naught that can be done to stop him. All who oppose him will perish.
At best, individuals with knowledge of trimentals can guess that the Omega will share some of their qualities.
Omega is unique, and his abilities cannot be anticipated nor replicated. Whatever he is or has done, there is only one way to find out what he is truly capable of.