The Mists of Erantia — G. Akella

Roman was never supposed to escape the locked plane that was his prison. And yet, somehow the impossible task became possible with the help of new friends, and despite the tricks of old enemies. Too intrepid was the demon driven by the fury of battle, the sorrow of defeat, the bonds of unbreakable friendship, and the longing for his beloved....

But when gods themselves join the fray, the chances of victory fall from slim to none. Just don't tell that to Roman, better known as Krian the Prince of Craedia, or to his friends, for their will to fight for the realm they now call home is inexhaustible, and fight they will to the bitter end....