He lives in the same quiet Southern town as Alvan Strict, alone in a dark house where no one can ever look at him.
Monsters always prey upon the vulnerable, and it so happens that human children are some of the most vulnerable beings there are. Poor things weak to despair and sadness, and no one ever listens to them. And those who do listen should not always be trusted.
Cecil was born to two monsters like this, and he cannot forgive himself for it.
He is not truly a living being, but an illusion made out of lantern oil and glitched code. He can feel things, think things, and do things of his own accord but he is not a person. Or at least that's the way he feels about it.
He came into existence after the Gameboy that held the monster called the Uncle was thrown into a river. The cursed object began to fade away as the Uncle died, but it hit a road block on its path to nonexistance. It landed in a sort of purgatory, the Unknown itself.
Was it fate? How else would this object manage to land in the middle of a forest of Edelwood trees, after the Beast had been vanquished? Did some unseen force decide that, no, fear and sorrow can never be truly defeated? For once the Beast died and his soul spilt with the oil of the lantern, it trickled away and began to fill the cracked screen of the Gameboy.
And from this mixture, a child was born. The new harbringer of hopelessness. But something was missing, or something completely new was added. When he saw sorrow and fear in others, he felt nothing but extreme guilt and empathy. He felt that he was to blame for all that went wrong in the world.
He ran, ran to the surface, the world of living flesh, and hid away in a quiet place where he'd never have to be seen. Unfortunately, he cannot run from the darkness he holds in himself. It's only a matter of time before he does something terrible.
Cecil is a very skittish, strange person who seems to switch from frantic, cryptic declarations of doom, to casual chatting about Nintendo games at the drop of a hat.
He avoids people and pushes them away, for he believes his presence brings sadness and misfortune. As a result, he is very lonely and stressed from the burdens he puts upon himself.
Cecil can sense feelings of dread, despair, fear, and sorrow in other people. He can smell it, see it, taste it, he actually can't ever escape from it. Some people and places give off stronger vibes than others.
He can also change forms, but only between two default forms. He doesn't like either of them.