it could be that xyor was led to the moon by dredgen under the pretense of a wedding and she was transformed into a wizard. Dredgen definitely knew enough about the darkness to make something like that possible. Ever since I read the black garden grimiore I've started to question if the guardians are truly good, they are dead almost immortal beings brought back to life for the sole purpose of killing

Or maybe even his widow who took up Thorn after he was killed and went to the Hive to avenge her slain husband!