Lunari, known as Luna, is the pet moomba of Guardian Corps member, Joshua Rush. He was given the moomba as a gift by his older sister around a year ago for no apparent reason other than he "needs someone in that lonely house", and he "wouldn't be getting a girlfriend any time soon".
Moomba's came into style after they were discovered near Mt. Caldare in a large group and, much like the sheep of Gran Pulse, didn't seem to have any dangerous intentions whatsoever. They apparently mutated off of another creature sometime in the past, though which one exactly is unclear.
Nevertheless, moombas tend to look after themselves more often than not and are somewhat of a cross between a dog and a cat in mannerisms; they're affectionate when the owner is there (provided they like them), but aren't entirely dependent on the owner and can look after themselves. They have shown some speech capabilities and can be trained to speak the odd word or two, but have no communication skills above that.
Because of their protective tendencies towards intruders, a moomba can be trained to attack only unknown characters in much the same way as a dog. They remember who to and who not to attack by tasting people's blood, and owners of moomba's tend to do this early on with people they know.