In 1358 DR, a warlock coven referred to as the Toril 13 done a ritual that cursed most tiefling lineages—those of demons, devils, hags, and rakshasas, among the Other people—with the "blood of Asmodeus", switching https://crithitceramics.com/crafting-the-perfect-tiefling-warlock-a-guide-for-all-ages/