The Chanters of Tremaris Trilogy- by Kate Constable

Book 1: The Singer of All Songs
Calwyn is on her way to becoming a full priestess of Antaris. She's content with her life there, though often restless. She doesn't realize how much she longs to see the world outside of Antaris until one day she discovers an Outlander man inside of their unpenetrable ice wall.
From this man, Darrow, she begins to learn about the other lands and other beliefs, as well as the new danger that threatens their whole world. The man that Darrow was running from, Samis, has hopes to be the Singer of All Songs, one who could use all the chantments and take over Tremaris with godlike power.
When Samis enters Antaris, Calwyn decides to help Darrow escape and then decides to go with him. She suggests that they try to gather different types of chanters together to defeat Samis. That's definately not an easy thing to do, since many of the lands outside of Antaris don't approve of or don't believe in the power of chantment. But their journey finds them allies, and so their mission is determined.

Book 2: The Waterless Sea
To Calwyn the desert is an entirely new landscape, and to Darrow it is a place of past sorrows. Though Calwyn and her friends are comfortable with the new homes and lives they've made for themselves, they wind up on a desert journey into a world of political unrest, a land where children with gifts are taken away from their families to a life of grim isolation.
An attempt to rescue two such children leads them to the heart of chaos in these strange new lands.

Book 3: The Tenth Power
Calwyn returns to Antaris, hoping for the chance to speak again with the priestesses she once knew. But Antaris has fallen on dreadful times, and there is a lot more danger lurking just around the corner than Calwyn bargained for.
Samis is still alive, and this time he has a new goal in mind, one directly involving Calwyn.

More by Kate Constable:

	Book 1: The Singer of All Songs Calwyn is on her way to becoming a full priestess of Antaris. She's content with her life there, though often restless. She doesn't realize how much she longs to see the world outside of Antaris until one day she discovers an Outlander man inside of their unpenetrable ice wall. From this man, Darrow, she begins to learn about the other lands and other beliefs, as well as the new danger that threatens their whole world. The man that Darrow was running from, Samis, has hopes to be the Singer of All Songs, one who could use all the chantments and take over Tremaris with godlike power. When Samis enters Antaris, Calwyn decides to help Darrow escape and then decides to go with him. She suggests that they try to gather different types of chanters together to defeat Samis. That's definately not an easy thing to do, since many of the lands outside of Antaris don't approve of or don't believe in the power of chantment. But their journey finds them allies, and so their mission is determined.
	Book 2: The Waterless Sea To Calwyn the desert is an entirely new landscape, and to Darrow it is a place of past sorrows. Though Calwyn and her friends are comfortable with the new homes and lives they've made for themselves, they wind up on a desert journey into a world of political unrest, a land where children with gifts are taken away from their families to a life of grim isolation. An attempt to rescue two such children leads them to the heart of chaos in these strange new lands.
	Book 3: The Tenth Power Calwyn returns to Antaris, hoping for the chance to speak again with the priestesses she once knew. But Antaris has fallen on dreadful times, and there is a lot more danger lurking just around the corner than Calwyn bargained for. Samis is still alive, and this time he has a new goal in mind, one directly involving Calwyn.