Earlier alife programs had worked by giving their organisms a limited set of commands and parameters, and seeing whether the way the subjects behaved was realistic. This was seen as an important insight into how real world organisms may function and evolve. Most interestingly, the Norns turned out to behave similarly to living creatures. By breeding certain Norns with others, some traits could be passed on to following generations. This meant that the Norns and their DNA could develop and ' evolve' in increasingly diverse ways, unpredicted by the makers. The program was significant as it was one of the first commercial titles to code alife organisms from the genetic level upwards using a sophisticated biochemistry and neural network brains.

Later games in the series introduced a third species, the Ettins.

In Creatures, the user 'hatched' small furry creatures called Norns into a world called Albia, and had to teach them how to talk, feed themselves, and protect themselves against vicious creatures called Grendels.