On survival or PS you get a generic fairy with the stats of one for lvl 20. I dont remember getting anything for beating sky city but I do remember you get 3 items from crystalline. A weapon, an armor, or a pet. Sometimes it is all 3 armors or another mix of the three. I never pulled anything great from either of these maps. Just wanted to be able to say it is possible. If you want a challenge try Aquanos PS on any difficulty higher than medium. The rewards are crap, but to me it is one of the more difficult maps to build. It is the only PS map that I havent beat on Insane.