Tiefling

Tieflings in Norewald is quite different from the original. Tieflings are people with hellish bloodlines, meaning other race's blood mixed with these but not limited to, demonic or devilish blood. Most examples are from Magic users that summoned a fiend or demon and somehow sired a child with the said hellish creature, either by carnal desires or magic experimentation. Whatever the reason how the child was conceived, the result is a person called a Tiefling. Dungeons and Dragons describes Tieflings: "To be greeted with stares and whispers, to suffer violence and insult on the street, to see mistrust and fear in every eye: this is the lot of the tiefling. And to twist the knife, tieflings know that this is because a pact struck generations ago infused the essence of Asmodeus, overlord of the Nine Hells (and many of the other powerful devils serving under him) into their bloodline. Their appearance and their nature are not their fault but the result of an ancient sin, for which they and their children and their children's children will always be held accountable."
Norewald is a closed world, where there should be no creatures from the outer planes. This means no Aberrations, no heavenly creatures and no hellish ones too. The world is encased with an incredible, impenetrable invisible shell that prevents entry by almost anyone or anything, physical or otherwise.
Because of this shell, sentient denizens variety in Norewald are rather limited as there are less to mix with. So therefore the appearance of an aberration like say, an Illithids (Mindflayer) or an infernal like Demons, fiends etc. are exceedingly rare. Not impossible though.
There are in fact creatures of the like that exist or existed, most are hunted and killed by the natives of Norewald be it it's native monsters or organizations like the Arganian empire's Sancti for example. These in perspective, Norewald Tieflings are quite different and untied from the normal convention and accepted material.