The Spathi are a cowardly race of "meta-mollusks" as described by Captain Fwiffo. Their membership in the Ur-Quan Hierarchy is a very dubious one, having been given the wrong straw so to speak by the mischievous Umgah. They live in constant fear of a non-existent phantom beyond the reaches of their most powerful sensors, called the Ultimate Evil.
They evolved on the lone planet of Epsilon Gruis I, called Spathiwa. At the onset of The Ur-Quan Masters, their planet is beleaguered by a race of ravenous creatures who enjoy eating Spathi, called the Evil Ones by the Spathi, so they live on the moon of Spathiwa until later in the game.