Through Trials and Towers (Tal'Avern Chronicles Volume 3) by Scott Borgman

Blurb:

As the harsh winter ends, Tal'Avern is on the brink of war. The great wall that stretched across the southern border of the Province has been destroyed and is engulfed in flames, but the fires won't burn for long. When they go out, the waiting hordes of goblins and Slaath will sweep up from the Ashlands and into the Province unchallenged. In the lands of Mar'Druk, the dwarves will be facing a relentless foe against the combined might of the united clans of orcs. 

What chance does the world have against such odds? What hope is there against armies who are led by a god that is bent on conquering the world? Against dragons that can't be killed, who bring death and destruction with their very breath? 

Varik, Chaz, Camila, and Wrinn begin their search for the lost towers of Zanimarith, where they hope to find the answers to defeating Visanith, while Jenna, Rhogar, and Esmara head off in search of a way to fight back against the dragons. 

If they fail, Tal'Avern will fall to the darkness that is poised to sweep north and engulf the entire world. The stage is set. The war is about to begin. And everyone has a part to play in it.

To check it out: http://www.amazon.com/Through-Trials-Towers-TalAvern-Chronicles-ebook/dp/B00VL9MCLE/ref=sr_1_11?s=books&ie=UTF8&qid=1440885371&sr=1-11&pebp=1440885383967&perid=19FEC74V12F23H1PVPSX#customerReviews