Legacy of the Last War
Source: Elemental Evil Players Companion
Genasi are extremely rare in Eberron, and although theories regarding their origins abound, even the genasi cannot say how their race came to exist. One rumor has it that genasi were once explorers of another race—perhaps dwarves—who were caught in a volcanic eruption of the Fist of Onatar, in the Ironroot Mountains. The force of the explosion, fueled by dragonshards deep beneath the lava, changed these beings from what they once were into genasi. Some arcanists hold that genasi are the creations of the powerful wizards of the Arcane Congress, experimental beings who escaped from their exhibit in the Floating Towers of Arcanix. There are also those who clainj that genasi are nothing more than random genetic mutations appearing among the offspring of humanoids who have had prolonged exposure to the malign influence of Khyber. Whatever their origin, few genasi live in Eberron.
Although rumors speak of the existence of a genasi village in the wilds of the Eldeen Reaches, genasi have no territories of their own. Most dwell on the fringes of human communities, avoiding their neighbors. The people of Eberron are familiar enough with magic that they don’t hate or mistrust genasi, but neither are they comfortable around the strange and clearly unnatural beings.