From Creatures Wikia
The Warpworlder Grendels are a genetic grendel breed by Grendel Man with a lot of wanderlust. They are practically addicted to using Warp Portals (or any portal, for that matter). They also have no problems with using teleporters, and if they wind up next to a portal when they are finished teleporting, it's all the better for them. As with the Cetus Grendels, they hit ettins to get starch. They will also eat detritus and food when hungry. They feel homesick when in bright areas, but their usually constant warping doesn't make that much of a problem.
Warpworlder Grendels are available from Grendel Man's section at Creatures @ CU7.