Over the realms of Kingdom Sky, circling in distant orbit, is the pale moon. There, carved into the mesas and vast seas of the lunar surface, are the crystallized memories of a primeval Guardian race: the Xyno. As if they were themselves alive, these crystals harbor a curious attraction to the worlds below. When the moon is full and the gravitic tides are at their most powerful, some of the crystals will wrest themselves free, and plummet into the kingdoms like falling stars.

Guardians exposed to the power of a crystal will undergo a mysterious transformation, mutating at once into a dark feline with iridescent wings. Ghostly lights trace multicolored patterns beneath their fur, and their feathers glow in shades of rainbow. Old personalities and memories remain, but the transformed Guardians will hear a new calling. More and more they will seek the night skies, flying in the light of moon and stars. Those who watch closely can see the faint luminescent trails they leave behind as they glide amongst the clouds.

But — the Xyno is a rare sight indeed. Those who catch a glimpse of the creatures often see them in small groups, congregating for some unknown purpose. Pure Hearts who have befriended them must often grow accustomed to their enigmatic natures. A Xyno is a powerful and loyal ally, however. No matter how distant they may seem, they will always step up to defend the realms whenever Kingdom Sky is threatened.