The Nephalem are an avian Incarnate lineage. All members of this lineage have wings, which they are unable to retract, giving them an angelic appearance. Members of the Nephalem bloodline are one of the few Incarnates that are unable to fully shift into the animal upon which their genetics are based. This inability is caused by a genetic defect that has proven to be more resilient than any transitioner would ever dare to admit.
When a Nephalem comes of age, I.e. assigned an Incarnate and has latent Nephalem lineage DNA, their wings begin to grow from their back and they reach a full wingspan of 3 to 4 meters in about 5 years. Flying is very much part of their culture and historically, pre-awakening Nephalem lived in the mountains of Feng in the north of Aohu as a means to have an inaccessible habitat to those that do not fly.
All wings of Nephalem are made of a substance known as coraphene, an organic version of graphene that is lighter than air but far stronger than steel. All attempts to reproduce this artificially have only been met with limited success. Contemporary industrial 3D printing can make similar materials but none are quite as durable. As a result, "natural" coraphene is highly sought after. The material is known as Engelstahl or Angelsteel on the black market.
Traditionally the wings of dead parents are made into armor and/or tools for their children. Heritage Angelsteel armor is even capable of tapping into the wearer's circulatory system and heal damage dealt to itself. The legitimate inheritors of such armor have no incompatibility issues being the children of the deceased donor.
Post-awakening, the Nassim family were discredited after Genecia revealed that they were not divine beings but merely Incarnates. This, in turn, caused an upheaval in the Gnost Quorum. Angel statues were defaced or smashed. A large number of references to angels in the holy books were rewritten. The Nephalem themselves became pariahs and entrepreneurial individuals went as far to start hunting them for their wings. Some of the Nephalem started to sell their own wings on the black market, becoming "fallen", all in order to reintegrate themselves into the new economy, find jobs and avoid harassment. A lot of these fallen can be found in the outer suburban sprawl of San Miguel. The Nassim family themselves have a self-imposed exile in San Miguel, though they were too proud to give up their wings. The leader of the Gnost Quorum, Saint Asa extended an amnesty to the Nassim Hierarch in exchange for them contributing generously to their local community. To which they built the imposing Simbulan Penitentiary which resembles a giant kneeling angel that can be seen as an iconic structure in the San Miguel skyline.