The destiny of the dead - Ian Irvine

Nish and his few remaining allies are trapped on the Range of Ruin, surrounded by the relentless army of his father, the God-Emperor. Nish's only choices are a humiliating surrender, or a suicidal fight to the death.

Yet Nish has to fight, and somehow he has to win, for the world of Santhenar faces a colossal threat - and Nish is a fighter in a land whose spirit was broken long ago.
A shape-shifting being by the name of Stilkeen has broken out of the void, and is preparing to wreak devastation. It has come to reclaim the stolen chthonic power that once bound its physical and spirit aspects together - and its fury is infinite.

But chthonic fire has already been released into Santhenar, and is eating its way through the Antarctic territories. Even if Nish can win the battle with his father, there may be no way to stop the fire, or Stilkeen, before everything is consumed.