the f***!!!! if this world works even remotely similarly to earth (physics wise I mean), then he made an explosion so strong it blew away the sun's light from a portion of the sky for, probably most of a minute, given they were far enough away to not notice the spell itself but still able to quickly enough reach him after the fact he didn't have time to clean up (which means it probably reached like 1/8th the way to said sun, possibly MUCH closer depending on what type of star it is, before it dissipated enough to stop deflecting light)
also, it wouldn't be the first time a manga pulled the "all the king's children are called prince for equality" routine, so yeah, 7th prince for now maybe, but (like several others before me) I'm not gonna be very surprised if "he" is actually a princess
@NephNep it's probably not as bad as it seems, it's a very small chunk of the sky, and unlike our world where it's been eroded through chemical contamination, their world probably has more than enough ozone layer left to cover the hole, though it might be a bad idea to be outside too much for the next couple weeks...as long as he does not make a habit of it, it should be fine
EDIT:
@NephNep assuming it was the heat that caused it, probably? but if it was mostly kinetic force generated as the magic pushed its way up instead then lingering heat issues wouldn't exist, also even if that was the case, again since the magic was channeled up and into outer space in a fairly short time frame, that *probably* shouldn't cause any major lasting damage, after all, the daylight more or less closed back up right away, also the sky is blue because of how light bends, not because of ozone