Any Creature that does not count as any tribe is considered a tribeless, or Generic, Creature. Only four tribeless Creatures were ever released; two were Super Rare (Smildon and Proboscar), and two were Ultra Rare (Ursis and Cromaxx). Smildon and Proboscar were seen in the show residing in Prexxor Chasm, and it is implied that Ursis and Cromaxx also inhabit the treacherous location. Only the Code Masters and players who have beaten them and earned a Prexxor Chasm scan as a reward appear to know about the Generic Creatures. Generic Creature cards are much like Generic Mugics- they are the same, silver color that Generic Mugics and Battlegear cards are.. Because Generic Creatures have no tribes, they may only play Geneic Mugic (unless other factors like a Heptadd's Crown or a Chorus of Cothica are involved to alter tribal allegiances).
Below the current creature Tribeless: