A Guardian Reborn - The Guardians, #3

Having survived his duel with Empress Hefrask, Grogaan now fights for his life, which hangs by a thread. To prevent him from being discovered by Imperial forces, Ellarna hides him the cave where their ships are parked, and protects them by magic. While in hiding, Ellarna discovers new gifts in the art of magic, ones greater than are currently known of by Guardian Master Taggash, and revealed to her by some strange creatures indigenous to Cassendra.
When Grogaan finally awakes, he breaks some devastating news to his fiancée; he has lost both his memory and his gift in magic. While on the road to recovery, he meets a mysterious stranger in an underground cavern, who has a profound impact on his life, but can Grogaan recover physically and mentally, and regain his memory and magical powers before the Hebradon Empire returns to the Ladorran Quadrant to continue their conquest.