The Wayfarer Redemption #6 : Crusader book by Sara Douglass

For countless millennia the Star Dance and the TimeKeeper Demons have battled their way across the universe, destroying innumerable planets, laying waste to civilizations across the cosmos.

Choosing the land of Tencendor as their last battleground, the demons break through the Star Gate. The Gate destroyed, all magic in the world is gone and the three races of Tencendor are plunged into a vortex of chaos, madness, and death.

Caelum SunSoar, son of the near-immortal Starman Axis and beloved ruler of all the land's peoples, is dead. Leaderless, those not killed outright or driven mad flee to the one place left to them, Sanctuary, a magical place created ages past to shield all who are good from the wrath of the demons.

There is for some one hope left: DragonStar, Axis's other son. Many believe he is the true StarSon, the only being that can save their world. Others are just as convinced that he is in league with the demons and will be their doom. Only DragonStar knows the truth and as he and his companions go forth to do battle he prays that he may convince all that his motives are pure.

What he does not know is that there is a traitor who plans to hand Sanctuary over to the Demons. A betrayer whose actions could force DragonStar to make a sacrifice so bloody and horrific that it could mean the destruction of everything that he holds dear in this life or the next.

And if he fails, he could doom Tecendor to an eternal hell.