[Coldsaturn]

"degree of fine/delicate control"
I don't think this is a spoiler since we're already talking about this, but in his spring card he snapped his fingers and changed the color of the flower crown MC had made him. That's how precise his energy manipulation is.
Hopefully we'll get to see more of his power in the third myth. We've already received a plot twist with his latest promise card, since we didn't know his Aether core worked like that, maybe we'll learn when he even got the thing stuck in his eye. I don't believe he was "born like that" for some reason.