There are the alien live forms in Civilization: Beyond Earth. The green icons represent an alien unit. They are in small, medium and very big sizes. They have melee, ranged and flying units, as well as 3 naval units. In general they will not attack, unless we attack them first. It is challenging to keep the aliens around as they are getting on the way of army and constructors. But they can be a good shield in early wars. In time they can even become friendly, and their color will change to blue. Also later they can be captured. The aliens roam around their nests (l) .