The Grudgebearer Trilogy Series by J.F. Lewis

Kholster is the first born of the practically immortal Aern, a race created by the Eldrennai as warrior-slaves to defend them from the magic-resistant reptilian Zaur.  Unable to break an oath without breaking their connection with each other, the Aern served the Eldrennai faithfully for thousands of years until the Sundering. Now, the Aern, Vael, and Eldrennai meet every hundred years for a Grand Conjunction to renew their tenuous peace... moreKholster is the first born of the practically immortal Aern, a race created by the Eldrennai as warrior-slaves to defend them from the magic-resistant reptilian Zaur.  Unable to break an oath without breaking their connection with each other, the Aern served the Eldrennai faithfully for thousands of years until the Sundering. Now, the Aern, Vael, and Eldrennai meet every hundred years for a Grand Conjunction to renew their tenuous peace.  While the tortures of slavery remain fresh in Kholster's mind, most of the rest of the world has moved on. Almost six hundred years after the Sundering, an Eldrennai prince carelessly breaks the truce by setting up a surprise museum exhibit containing sentient suits of Aernese armor left behind, never to be touched, lest Kholster kill every last Eldrennai. Through their still-existing connection with their ancient armor, the Aern know instantly, and Kholster must find a way to keep his oaths, even those made in haste and anger. While Kholster travels to the Grand Conjunction with his Freeborn daughter and chosen successor Rae'en, his troops travel by sea, heading for war. less

Rae’en has taken her father’s place as First of the practically immortal Aern, a race created by the Eldrennai as warrior-slaves to defend them from the magic-resistant reptilian Zaur. Freed from all Oaths by Kholster’s death, Rae’en decides to wage war on the Eldrennai anyway out of rage and grief. The war between the Eldrennai and Zaur has begun. Bloodmane, leader of the now independent mystic-warsuits, has underestimated both the sheer numbers of the Zaur and their field leader General Tsan... moreRae’en has taken her father’s place as First of the practically immortal Aern, a race created by the Eldrennai as warrior-slaves to defend them from the magic-resistant reptilian Zaur. Freed from all Oaths by Kholster’s death, Rae’en decides to wage war on the Eldrennai anyway out of rage and grief. The war between the Eldrennai and Zaur has begun. Bloodmane, leader of the now independent mystic-warsuits, has underestimated both the sheer numbers of the Zaur and their field leader General Tsan. As the warsuits  prepare to assist the Eldrennai  in the  defense of their Watch cities, the Zaur warlord, Xastix, launches the bulk of his forces at the Vael in an attempt to cut off all outside help.Prince Rivvek, having been accepted as an Aiannai (Oathkeeper) before Kholster’s death must claim the Eldrennai throne by completing the Test of Four so that he can enact his plan to save as much of his kingdom as possible.  Meanwhile, his brother Prince Dolvek hatches a plot to enlist the aid of the plant-like Vael to defeat the Zaur horde who are in league with the decapitated head of a dethroned deity.From the Trade Paperback edition. less