All we know of The Dreamer's appearance is his dream-image of himself. His personality is Largely unknown, although he seems to generally be a good person. However, he does happen to have an evil side which keeps eating him (and hence, itself) and stopping him from proceeding.
This gigantic, horrifying monster was actually The Dreamer himself, trying to eat himself.
The Dreamer found himself in a very strange nightmare, In which he had to explore a Twisted and evil world, where even the buildings wanted to kill him or eat him. After .::cleverly getting past a gigantic, evil version of himself, he explored a strange city. Storefronts had teeth and skyscrapers were monsters.
The Dreamer is ready to do whatever it takes.
The Dreamer, as far as we know, is still attempting to escape his dream. (Miscellaneous game: "City of Dreams")