Aster's Angel form.

after some time as Bastion's conscience, Aster came to realise there was more to being a Nephilim than the halo above his head.
after the little wolf helped Bastion gather the courage to face a difficult problem he'd been having, the hybrid blood in his veins boiled, and in a blast of intense light he grew a pair of magnificent wings on his back. this left Rilda jealous as he had not awakened his Cambion bloodline activation yet.

while this new power made Aster stronger and faster, it did not make him any larger, but who needs to be big when you can fly?

Aster was able to alternate between his Angelic and regular forms at will since that point.