It's visually much like Terastallization...what usually happens with those crystals. But there aren't any of them around here as far as I've seen. It may mean we're far from Paldea.

[Or at least the crater? Which works out perfectly for him.]

That is a Rookidee! They are pure Flying-type Pokemon, which is quite unusual. But if it ever evolves all the way to Corviknight, it will become a Steel-type as well.