Sally A. Laughlin 
Dragon Fire [EPUB ebook] 

A union is formed between a master demon and a deadly witch to become the most powerful beings in Mystovia.
After they capture Chan-Draa — a potent Seer of the Arega dragons — and take her to a forbidden city deep in pirate territory, they begin to absorb her powers using a Witch’s Choker. Once all the glowing stones die, so shall Chan-Draa.
It is up to Mac and Kess, along with their friends, to travel across a treacherous desert and into the dangerous pirate stronghold to rescue her. Racing against time, can they get to Chan-Draa in time?
A compelling fantasy adventure, ‘Dragon Fire’ is the fourth book in S.A. Laughlin’s ‘Warriors Of The Mystic Moons’ series.