Being that The Secret World is set in a world of myth and legend, It’s got one hell of a collection of creatures to call upon – including many of the creatures of Hell I suppose.
The obvious ones all make an appearance, Zombies, Vampires, Wendigos & Mummies are all to be found in this game. Cthulu’s friends the Deep One’s also make a showing very early on in the game.
While I have not met him in the beta, apparently even the bogeyman is real and still out to get you after all these years.
There is so much more to this game that has been announced so far that I would imagine that if you can think of a terrible nightmare from your childhood, it will probably show up in the game at some point.
More information on the Monsters can be found at http://www.thesecretworld.com/world/monsters