Treasure & Treason by Lisa Shearin

An ancient power.
Hidden for millennia in a legendary city on an uninhabited continent, the Heart of Nidaar can harness the forces of nature itself. In the wrong hands, the artifact is a weapon that can command the power of the earth and seas to destroy all life. Just the type of power a sinister goblin brotherhood finds irresistible. In their hands, kingdoms will be forced to surrender to their rule.

A team of royals and rogues.
Chief mage (and nearly rehabilitated practitioner of black magic) Tamnais Nathrach is the perfect goblin duke to stop them. Along with elf pirate Phaelan Benares, these two have a roguish plan to sail to Aquas and snatch the Heart of Nidaar before it can fall into the wrong hands. After all, stealing hearts is what these two do best. Who cares if goblins and elves have been in a near constant state of war for centuries? This common enemy is enough motivation for some teamwork and a little professional competition.

The adventure of a lifetime.
Perhaps Tamnais and Phaelan have forgotten one small fact. Expeditions that sail to the continent of Aquas never return. It’s a blighted wasteland filled with creatures from nightmare and Tamnais might have failed to mention that the Heart has guardians, an ancient race willing to use deadly force to keep themselves and the artifact hidden. Alliances are tested, courage is challenged, and nothing less than the future of all life in the Seven Kingdoms is at stake in the deadliest—and most competitive—treasure hunt of all time.