They obtain energy by absorbing it from organic matter- via touch, instead of actual eating. However, they do have a fully-functional digestive system that allows them to eat actual food.
They speak telepathically, but cannot read one-another's minds. Some can also see the past/future, use telekinesis, and have psychokinetic abilities [ie: pyrokinesis].
They choose their form, but have one thing they can't change- color scheme. They are all born with black skin and a specific set of colors/a specific color that they use to identify themselves. While the vast majority have a single color (with which they can use any shade of to color themselves), some (such as Xenna) have several.