Bakemono are basically the Asian equivalent of the European goblin. Their appearance varies greatly, with colors ranging from cobolt blue, bright red, orange, or any other odd shade. They often have strange features such as hooves, small useless wings, fur, feathers, horns, tusks, scales, etc.
They're more known for their numbers than their ferocity, but a horde of bakemono would spell trouble for any samurai who met up with them. In Rokugan, the world of Legend of the Five Rings, bakemono were created by Fu Leng, and were his first, flawed attempt at making a powerful servant. In the first few storylines of the game, they weren't as dangerous as the Oni or Ogres but in the recent storyline, they've become a real threat in and of themselves. (I believe they're being led by some character named Omoni.)