The Riilebs were a sentient species of humanoid insectoids that were indigenous to the planet of Riileb. Members of the species were relatively tall, with gray, knobbly skin and two antennae, which were capable of detecting changes in the biorhythms of other organisms. Using their antennae, the species could detect the mood of those around them, which made them good at setting others at ease and so resulted in others perceiving the Riilebs as a likable people. They also possessed four nostrils on a nose that was much flatter than a Human's; two nostrils were for inhaling and two were for exhaling.