Mu'Ursis is a Mu Guardian in need of rescue. He can be found on the Recover the missing mystic and discover the reason for his abduction mission from Magus Mu'Drakhan. He spawned as a Pet of the level of the mission owner +1, having the correspondant ammount of Hit Points, and a faction of Arachnos. You don't need him to survive the mission, and there's not apparent penalty if he dies during it.