Monsters are the antagonists in both ESCaPE 1 and 2. They don't exactly have names yet, but have been given nick-names by the game's creator. The total amount of monsters (including from both games) are 5.
In both games, the monsters resemble something human-like, and some have very sharp teeth, and blood-shot eyes.
All the monsters except Skele and Bloodmouth have teeth, and they all are a yellow-ish color. Some of the monsters even have blood splattered on their teeth, too.
Bloodmouth and Skele have no teeth at all. While Bloodmouth has a jaw with red strings (possibly blood, hence the name given), Skele has a tall jaw with no teeth. Unlike the other monsters, Skele is the only one where you can see every part of it's jaw.
The whole idea and appearance came from one picture. It is unknown what is the picture or who made it, and it might be never known. The creator then drew more that resembled the picture he saw/made... and then put them into a game,
The creator, when drawing these, never wanted to put these monsters into the game, but then shortly after, the creator decided he wanted to make a game, and release it to public. He didn't have an idea, until he saw the images of monsters he'd made.