You are the descendant of both celestial and fiend, however that is a broad list.

Celestial:Choose between death pact, battleforce, and firemane. These choices determine the type of damage your Celestial Revelation will deal later on.

Fiend:Choose between demon or devil. This choice determines what languages you learn and how you act when your Fiendish Revelation is active.

Choose between death pact, battle force, or fireman.

The bloods within you grant you a "pair" of mismatched wings, one angelic and one fiendish.

Your fiendish side grants you a set of horns and clawed hands, these can be used as natural weapons. Unlike other races with natural weapons these count as melee weapon attacks instead of unarmed strikes.

The bloods inside you grant the same resistance they do to Aasimar or Tieflings, granting you resistance to fire, necrotic, and radiant damage.

As an action you empower your fiendish blood strengthening your fiendish features. For as long as you can concentrate(works like concentration for spells) your horns have the reach property, you become one size larger, your tail grows spines and you gain a tail attack, both your horns and claws deal double damage, you gain immunity to fire damage and the way you act changes depending on your Fiendish Ancestry. 

Both Fiendish and Celestial Revelations can be active at the same time. When both Revelations are active you no longer act like your fiendish ancestor however you have disadvantage on the concentration saving throw.

Revelations take a toll on the body and can't be used too often, each Revelation can only be used once per fight. Concentration ending on revelations causes your blood to return to a depowered state causing a turn of lethargy for each revelation, similar to when a haste spell end.

As an action you awaken your celestial blood strengthening your angelic features. For as long as you can concentrate your flying speed increases to 60ft, all of your attacks deal extra damage equal to your level dependent on your Celestial Ancestry, and you gain immunity to radiant and necrotic damage. If your DM allows it you also gain truesight out to 30ft.

Both Fiendish and Celestial Revelations can be active at the same time however you have disadvantage on the concentration saving throw.

Revelations take a toll on the body and can't be used too often, each Revelation can only be used once per fight. Concentration ending on revelations causes your blood to return to a depowered state causing a turn of lethargy for each revelation, similar to when a haste spell end.

Like both Aasimar and Tieflings you have 60ft of darkvision.