Ancillius are Maxis-made creatures, present in the final game. They are not good at many things, but they excel at the things that they can do.
They are herbivores, but they can put up a good fight. Their tough skins are covered in hard shells, which make it difficult for aggressors to sink their teeth or claws into the Ancillius. If they notice any predators, they will charge, ramming headfirst into the creature. While the other creature is dazed, it will either bite at the creature or run away.
The Ancillius are rather simple creatures, and rather easy to impress in most instances. Their only social talent is singing, but they are masters of melody. Many creatures have been driven out of Ancillius nests by accidentally insulting the beasts with unsatisfactory tunes. Very few other species can match the vocal skills of the Ancillius.