The Nornverter is an application bundled with the original release of Creatures 2. It allows you to convert norns from the original Creatures to the Creatures 2 format. Norns are not technically converted as such, but rather the sprites, name and a few other characteristics of the original creatures are "overlaid" on a standard Creatures 2 genome base. This means that converted creatures will no longer be sick or pregnant. It should also be noted that people have reported that these converted norns are more intelligent than the standard Creatures 2 norns.
Grendels, ettins and shee will appear as norns, because in Creatures 1 there was no genetic code to determine what species a sprite was (as there is in Creatures 2), and this was determined by the creature's genus. As norn is the first available entry for this new attribute, it will be assigned to all converted creatures.