The Mantis planet was an otherwise unnamed planet about a day's travel at warp speed away from Angoma, somewhere in the the galaxy's Alpha or Beta Quadrant. It was the homeworld of the Mantis species and appeared blue from orbit.
In 2266, Mantises abducted a landing party from the USS Enterprise. David Bailey followed the source of the transporter beam to the Mantis planet. A rescue party armed with non-lethal weapons landed a space bug near the Mantis zoo and stormed it to search for their missing personnel. (TOS comic: "Beware the Beast")