Carrying the taint of evil in their very souls, tieflings are persecuted and
feared in most parts of Faerun. Many with the more obvious signs of demonic
kinship are killed at birth, and even those with the less obvious of traits
are often killed by their own parents, who are horrified at the demonic
lineage of their child. The tieflings most likely to survive birth and
childhood are those raised by the indifferent, those who seek to redeem the
child, and those so evil themselves that they don't care.
Tieflings look human, save for one or two distinguishing features, such as
fangs or pointed teeth, or glowing red eyes, small horns or red skin to name
a few. Because tieflings can be born of many evil outsiders, it is hard to
tell any relation, as even two tieflings descended from the same Devil may
look radically different.
Most tieflings gravitate to the arts of the rogue, though there are many too,
that become wizards and clerics in order to summon and deal with their Lower
planer kin, as well as to enhance their own innate abilities.
Please note that your tiefling should not have wings without taking the
relevant feat first or an approved application for them.
Unless a planetouched character's traits are overtly obvious or they have
made it known, you should not roleplay as automatically knowing their
race/heritage. Rather they are just odd looking humans. One should also
consider whether they have a mask, hood, or armour that would further obscure
their features.