Tieflings, Aasimar, and other Weirdness

Legends tell of certain humans born with the mark of extraplanar entities on them, with fey features, or some other unusual physical or spiritual aspect to them. Some scholars postulate that such things may have been common in the old Adastrican Empire, where it is said that mortals often sought out contact with those from beyond the material plane.
In modern times, such things are almost completely unheard of, but most humans and halflings believe that anyone touched in this way is under the patronage of Gods or Demons, and destined to be a party to great events. They may react to such individuals with fear, deference, or enthusiasm, but few will be indifferent. Though dwarves tend to view all such personages with mild suspicion, the elves seem to find such things a part of the natural order.
In any case, such individuals will always be remarked upon and can become famous (or infamous) merely as a result of their unusual heritage.
There are no communities of such people, as they are singular, almost unique events.