From Creatures Wikia
The Nightmare Beasts are a set of four Grendel genomes made by Grendel Man. All are noticably agressive, have the "angry" expression permanently fused onto their faces, and enjoy hitting Norns and Ettins (Hence the term "nightmare beast").
- Fire Beasts use the Blood Grendel sprites. These monsters love the heat, in fact, they need heat to breathe. They don't hassle Norns much, they prefer to attack Ettins.
- Water Beasts are gilled, but can live for an extremely long time on land. They like to hit aquatic norns and ettins. Critters taste good to them. But as they don't come across gadgets or machinery much, they either hit Norns or ettins or play with a toy. They also use the Blood Grendel sprites.
- Twilight Beasts don't eat. They get all the nutrtion they need from physical contact with other creatures (starch and protein from hitting Norns and Ettins, mating brings in fat). They are also unusual because they can breed from birth. Light will not kill them, but light does make them tired. They use the Zwergbunt Grendel sprites.
- Tempest Beasts do not sleep. They like to chase weather when bored for some odd reason. They are immune to all diseases. As well as chasing clouds, they also like to chase critters, play with toys, and hit Norns and Ettins. They use the sprites of Zwergbunt Grendels.