Key of Memories — Meg Hendry

Cadrenti once had a connection to the depths. Several Cadrenti want that connection restored. They plan to free Orivitus from the depths. Helen is their way to do that. The Four Knights must help stop a war Aminis won't be able to win, while also fighting the will of the swords meant to bring about the Knights of the End. Key of Memories is a novella.