How Many Mouths
The villain now known as The Mouther was not always a beast. He was mortal once, back when his form did not make such a mockery of humanity. He came from a kingdom so far to the South its name is unknown in these lands, full of ambition, and already a marvellous wizard. He came to see the wonders and the ruins left behind by the greats that came before him. He trudged over every inch of Coraleith's abandoned isle, tasting the dirt and the flowers, trading whispered secrets with the breeze. He found a secret scroll in the ruins of Drakdagor's tower, before leaving what was left to the upstart, Harlan Blackhand.
He was searching for something, but at the time, no one knew what. Only later would the twists and turns of his reasoning become obvious. When the bluish hue spread all across his countenance, all could see which mantle of his predecessors he had taken up. But there were no multitudes beneath his skin. There is always only ever one man inside The Mouther, no matter how many mouths he can speak through.
But power has a price, of course. Where other, lesser, wizards may toil industriously to provoke new arcanas into this world, The Mouther is not bound to a single plane, and he must align himself with so many other worlds in order to create — or become — something new.
To that end, he has become as unto an infection — a disease festering at the heart of civilizations. He has corrupted the interiors of many cities in his unnaturally-long lifespan, and has his sights set on more still. For if The Mouther must put more time and effort into advancing his magics than other most other wizards, then he must also have a secure laboratory in which to do so. He is not above coercion, violence, and arcane mind control to get his way. He is not above building a cult in his honour, to be worshipped by loyal minions who secure his place within an urban metropolis, so full of would-be subjects for his studies and could-be successes for his experiments.
And yet, as much as his research requires stealth and social manipulation, The Mouther is still his own worst enemy. He has lost much of his human form, but few of his human vices. He still revels in pleasure, even as every human around him finds him revolting both in character and in physique. With his lusts and his gluttony in no way diminished, he must magically manipulate people around him into providing for his hungers, instead of seeking out ways to satisfy them the way someone who can pass for human might.