Beltaine

Plane-touched beings are not inherently uncommon in Archaios, though most of the lands peasantry will likely go their entire lives without seeing a genasi, tiefliing, or aasimar. Beltaine, on the other hand, are a plane-touched race that even some of the most learned of Archaios have scarcely ever heard of. 
Beltaine exist somewhere between fire genasi and aasimar: they bear the mark of the Plane of Fire, but also that of a celestial who makes his home there: Logira, a deity of the Fire Domain. Indeed, Beltaine are one of the only known sapient species that can trace their origins back to one specific deity.
Beltaine were Logira's solution to his dwindling significance in a world that no longer revered the "rudimentary" elemental domains. Having witnessed what could happen when a mortal being took a piece of Logira's immortal essence into his body in the form of the infamous Battle of the Fire Plains, the god opted to do it on purpose; effectively building an entire family of devoted followers.
It took some time, but eventually Logira was able to perfect the ritual needed to imbue strength within a mortal child and have it be enough that the power was significant, but not so strong that it burned away the mortal's corporeal form. It then took a few more tries to create a Beltaine who's temperament and disposition suited Logira. Eventually though, he was able to create a steady flow of new Beltaine, all of whom added to his collective strength both by their very existence and their rekindling of the old ways. A dynasty of Beltaine even ruled the kingdom of Adelden during the 6th and 7th centuries of the current age.
Eventually though, Logira became paranoid of losing his children, as many of them had a propensity for burning out in a blaze of glory, and gathered them together in a Paradise of his own making on the Plane of Fire. There, his children could live in safety and comfort while Logira bided his time and await a new opportunity to again expand his influence.
Currently, there are only at most a few hundred Beltaine known to exist, and most of them still reside on the Plane of Fire, though some were inspired by the sorcerer Eladan to aid The White Tower Alliance in their battle against Cataclysm.