This article contains plot details from the latest book.
Frosters are elves with the special ability of cryokinesis. This means that they can manipulate ice particles in the air to freeze whatever they want. In the first book , Dex and Marella were tested at Foxfire to see if they may be frosters by getting stuck in a very hot room for the whole period. Frosters can also cover themselves with ice as a disguise as seen in Neverseen when Squall (Juline) does it. Dex describes frosters as a useless ability, even though his own mother is one.