Prince of the Godborn — Geraldine Harris

In the first part of 'Seven Citadels', Prince Kerish, pampered favourite son of the Emperor of Galkis, and his half-brother Forollkin, are sent to find seven sorcerers who each hold the key to a gate. Legend says that that the seven gates imprison a Savior, who alone can save the embattled Galkian Empire and its Godborn rulers. In the dangerous world beyond Galkis, Kerish is forced to depend on his soldier brother. The prince soon discovers something that will make their quest much more difficult--if a sorcerer surrenders his key, he also gives up immortality. When the first sorcerer turns out to be a benevolent philosopher king, the brothers begin to question whether the cost of saving Galkis is too high.