The Dark Remains. Book Three of The Last Rune

From a brilliant fantasy master comes a tale of astounding magic, unrelenting evil, and redemptive courage. Travis Wilder and Grace Beckett have returned to modern Earth to get medical help for Beltan, a knight from the otherworld of Eldh. But as Beltan lies unconscious in the ICU of a Denver hospital, a shadowy organization plots to kidnap him, and sinister forces of dark magic cross the boundary from Eldh in a murderous search for Travis and Grace.
Meanwhile, in Eldh, a young baroness, her witch companion, and their mortal and immortal friends journey to a dying city, there to confront a nameless evil that has begun to annihilate the very gods. Somehow Travis and Grace must save Beltan and themselves, then make their way back to Eldh. For only there can they hope to defeat a demonic enemy that can shatter time, devour space, and turn existence into nothingness.