Ice Crown — Andre Norton

Offlas Keil and his niece, Roane, had their orders: to land on Clio and search out its treasure.

Clio was a closed planet. Settled centuries ago as a Psychocrat experiment, its colonists had been brain-cleared, implanted with false memories -- and conditioned to obey.

Keil and Roane touched down at Reveny, one of Clio's more archaic kingdoms. Roane didn't know it at the time, but she was to form an alliance with Reveny's Princess Ludorica in a search for the greatest treasure of all -- the strange, the mysterious, the all-powerful ICE CROWN.