From Creatures Wikia
The Demonic Grendels are a genetic grendel breed made by Edash. They are extremely aggressive, hunting down hapless norns and beating them to death. A Hardman Norn, however, may be capable of killing a demonic if he/she can strike fast enough. Another, similar genetic breed, also made by Edash, are called Kamikaze Grendels. Unlike demonics, these fast age, and die after killing a norn, or at the least giving him a good beating.