Black Grail — Damien Broderick

A millennium from now, global warming has gone into retreat as the Sun's dynamics convulse. The great ice returns, driving humankind back to its primitive origins. Here, bands of brutal warriors wage war in the bitter cold. Xaraf Firebridge, powerful young son of a barbarian chieftain, enrages his sire by adopting the pacifistic doctrine of an outland mystic, Darkbloom. Before he can break his vow and slay his father, he is drawn into a temporal wormline and flung a further million years into the Earth of the Failing Sun.

Clever and determined, Xaraf wanders landscapes haunted by prospects of doom and overseen by a trio of godlike Powers. Since childhood he has dreamed of a beautiful young woman. His fate, he sees, is to rescue her from captivity--and perhaps save the whole world, now moved into the outer solar system and lit by a string of tiny orbiting suns.

He has yet to meet his true foe, the dragon whose history stands opposed to humankind's. But which will prove to be this world's mythic Galahad?