From Creatures Wikia
The Mecha-Grendel is a toy mechanical grendel that comes with both the Hardman Norn and Banshee Grendel packs. Its only purpose is to entertain and relieve the anger of young Creatures. When activated, either by a Creature or the Hand, it grunts and jumps about and squeaks in a comically fake way.
As children, Hardman Norns seem to find this toy fascinating, but as they grow older, as with most toys, they become less and less interested in it, and start looking for the real thing!