J.M. Briggs 
The Iron Urn [EPUB ebook] 

Arthur is dead, but the Light is now in control of his body and determined to cut the Iron Realm off from the Tree of Reality. Representatives of the species dwelling on Earth join the mages to discuss the danger of the Darkness and the Light’s proposal. Still, Alex knows that severing their world’s connection to the Tree of Reality is not the answer. Turning to her past, Alex leads the mages to Wyoming and a Medicine Wheel she hopes has the key to stopping the Darkness.

Akule was a hunter and warrior for his band and tribe. He had a wife and children and was content. Yet, his eyes turn to a strange dead spot growing in the lands he calls home. Dreams and strange visions are his only guidance against this devastating Darkness dripping through the sky. Staying behind when his tribe leaves, Akule knows in his soul that he must stop the tide of destruction before it is too late.