The Namura Stone — Gillian Andrews

Book Six in the Ammonite Galaxy series:

Six and Diva are coming to terms with family life on Xiantha, but on the other side of the galaxy storm clouds are gathering.
The Dessites have managed to reach Enara, and have proposed an alliance to conquer both Arcan and the lost animas.

Suddenly Arcan finds himself trapped on the Dessite homeworld, fighting a losing battle to survive...

... And everything changes.