Firstborn of the Sun by Marvellous Michael Anson

In Oru L'ore is the only one without agbára - the ability to harness power from the sun. And must conceal it from everyone. Including her best friend, Alawani.

But when the gods declare Alawani an Àlùfáà, he must be stripped of his power in a brutal trial likely to kill him. Unwilling to bear his death, Lóre vows to rescue him.

But in a desperate attempt to channel agbára an icy magic pours from her hands; a power she learns originated from a forbidden, secret land beyond the walls of Oru.

One where she and Alawani must now seek sanctuary and discover a secret that could bring the Kingdom to its knees . . .