The Curse of Keldarin refers to the banishment of a Gelvani onto the Mortal World by Gelthena. Gelvani have eternal souls, but not immortal bodies. Upon Aelvanis they are instantly healed, and thus they do not die, but on the world of Naeja they can die. Gelthena cursed all of the Sixth Blood to reside upon the Mortal World until they redeemed themselves in her eyes. All Gelvani, even those born upon the Mortal World, must await The Call of Gelthena which will summon them home to Aelvanis. Those who die before the call must have their remains given the proper rites by another Gelvani else their soul will be cursed to reside in Neth-Noril for all eternity. Those who hear the call and ignore it will eventually become one of the Lost, who can never return to Aelvanis.
The Call of Gelthena is not the same for everyone. Some hear the call early, after only a few hundred years. Others may go nearly a millennia before hearing it.