A Grettin is a crossbreed (usually made using the gene splicer) between a Grendel and an Ettin. As Ettins do not naturally exist in Creatures 1, Grettins are therefore usually confined to Creatures 2 and Creatures 3 - in Docking Station, they can come through the Warp from time to time but without C3 being installed they will either appear invisible (if you have no third-party Grendel or Ettin sprites installed) or will default to whatever is available. See also: Grenorn, Nettin