Of Dragons and Stone - Grayce Tara

Five years before the events of Mountains of Dragons and Sacrifice, Clarissa is sacrificed to the dragon. But instead of the dragon, she is rescued by the dragon's steward Dorrian.

This companion book features the novella Night of the Dragon Steward, along with short stories under the heading The Dragon, which give snippets from Evander's POV. This companion book is best read after Mountain of Dragons and Sacrifice, as it contains spoilers for that book. 

The ebook is available from the author's newsletter.