Haven faction discussion.

Too bad for the Incas, but it seems there were such "messengers of light" before, and only later did they found a church, etc. (+ they also needed to come up with a name for a mage hero among humans).
This unit will most likely have magic, because she doesn't hit the enemy up close with her fist. It would look silly if a girl punched a titan or a devil.

As for the artwork with the flying girl, it is quite possible that this was one of the variations of this unit, or that this girl can transform into this thing and become a combat unit.