My head canon for it is they were an exiled researcher with plausible meteor magics within the Fruman walls, and they received some sort of curse or defect from the meteor's magic. The Fruman government catches wind of it and decides to send them off to Wynn, instead of just outright killing them, considering the only people with magic are the royals of Fruma. Kind of makes me think that the Fruman royalty has somehow managed to utilize cosmic magic to its fullest, since we really don't have an extensive theory of how the meteors effect the minds of humans. The only effects present for humans are the warped mind in star thief--a very weak minded individual--and some enemies who fall under the same boat as the thief. (Mention any that i've missed.) It wouldn't be too far of a stretch to assume beings of great power--more so great minds--would be able to utilize the meteors/any cosmic magic to its fullest.