The Bones of Makaidos by Bryan Davis

Book 4 of Oracles of Fire

Summary:

As The Bones of Makaidos begins, a wall of fire protects the inexperienced villagers of Second Eden from a planned invasion of dragons and Nephilim, but how long will the flames last? Billy, Walter, Ashley, Elam, and the faithful dragons help the people prepare, but they are woefully outnumbered and will have to go back to Earth and recruit the humans who have the ability to revert to their former dragon states. In search of aid, Billy escorts Acacia, an Oracles of Fire, through a dangerous volcano portal. 

Sapphira, Acacia's Oracle sister, stays in the underworld with Bonnie and Shiloh, waiting for the signal to emerge and join the battle. With Hades and Earth locked in a catastrophic merging of their two realms, Arramos, evil incarnate, plans to use Bonnie to add Second Eden to the convergence, thereby drawing his forces to Heaven's Gate, where he hopes to gain access to divine authority.

Arramos has two secret Sir Devin, the greatest of all dragon slayers, lies in wait to destroy all dragons and their offspring, including Billy and Bonnie; and Mardon, a brilliant scientist, knows the secret to the Oracles' indestructibility, and he has devised a way to steal it from Acacia, thereby draining her strength. Meanwhile, Semiramis, Mardon's mother, comes to Second Eden and provides Billy with a wealth of information about Arramos's plans, and with every subsequent challenge, her words are proven true. But can she be trusted?

With mysteries abounding and an ultimate battle looming, every decision could mean the difference between survival and catastrophe, and only a prophesied sacrifice can stop the onslaught of evil. But who will be the sacrificial lamb? 

Opening Lines: 

Mardon stood at the edge of the precipice and peered into the chasm. The sheer rock faces on each side plunged until they seemed to meet in the apparently infinite depths. Stepping back, he turned to a lady draped in a red cloak, Semiramis, her hood lifted over her auburn locks. "Mother, how do you propose that we descend?"

Lowering her hood, Semiramis gazed into the bright sky. "Arramos said he would show us the way during Second Eden's eclipse cycle. Since that eve is upon us, he will fly here soon. He is quite anxious to send us into the world." 

A crystalline egg orbited Mardon's head, flashing crimson light from within. As it stopped in front of his eyes, tis familiar voice, Sir Devin's voice, penetrated his mind. "Will you trust the instructions of a dragon?" Its eyes, no more than two reddish ovals, blinked. "Arramos is the most devious of the accursed race."