This is Skyler's battle dress. She switches to it in a flash whenever she enters combat; it's a lot more maneuverable than most of her other outfits. Her standard necklace is not visible in this picture; it's actually in the form of the wand that she is holding. It also has a staff formation. The special gem amplifies her magical power and enables its use in non-Avian lands.

This outfit takes a bit of inspiration from the Dark Flier unit class of Fire Emblem Awakening.