Transdimensionals

Transdimensional is a catch-all-term for a variety of creatures encountered believed to be denizens of other worlds and realities. Most appear to be organic, like human beings, but some defy logic or common physiology. 
Categorizing them is difficult due to their alien biology. As one not-so-wizened Adept put it, "if it looks like something out of Star Trek, it's probably a Transdimensional."