Muir is a large crab-like alien with a heavy, armored shell and large pincers, as well as telepathic tentacles. Molly and Jordan initially mistook it for a native Ōban life form until Prince Aikka told them Muir was one of the nine finalists.
Muir flies in what appears to be a giant, flying horseshoe crab, with claws and tentacles similar to its own, and a strange retractable fin in the back that discharges energy spheres. While racing, Muir sits atop a large, liquid-filled globe, containing the body of its mate. It is also revealed that the tentacles on Muir's back allow it to communicate telepathically and appear to be highly prized as a hunting trophy.
In Monstrous Like Muir, Molly discovers that she isn't the only one who wants to bring back a loved one; Muir's mate was killed by alien hunters who wanted her tentacles and left her for dead. Muir hopes to win the Ultimate Prize to bring her back to life.
Muir chooses not to take part in the final race after learning the prize doesn't have the power to resurrect his mate. After the race ends he returns to his home planet.