Mindflayers: A great species from D&D that I'd love to see in JADE. Give em mindcrafting powers like mental shield and telekinetic blast. Give elder mindflayers access to teleport and greater telekinetic blast. They live in large underground communities that revolve around an elder brain. Quests involving them could be freeing humans from their twisted experiments, or destroying the elder brain itself.
If they're ever incorporated, you have to throw in brain bugs too. Little parasites that they use that burrow into the brains of other creatures and control them. So when you encounter them there would be gangs of controlled humans protecting them. This way they could also have agents in the outside world deceiving you.
http://en.wikipedia.org/wiki/Illithid