Wreckers Gate by Eric T Knight

It’s a suicide mission with only one purpose. The king wants Wulf Rome dead.

When General Wulf Rome gets his orders to chase the marauders into the fiery hell of the Gur al Krin desert, he knows the king has finally decided to eliminate his too-popular general. What he doesn’t count on is causing the apocalypse.

Somehow Wulf Rome survives both the marauders and the desert, but he ends up in a lost catacomb deep beneath the desert sands, where he finds a strange axe embedded in a massive, unnatural wall. When he pulls it free, he unleashes a nightmare of epic proportions. Monsters and diseases plague the land. There is no defense, no enemy even to strike against.

Out of the chaos a mysterious stranger calling himself Lowellin appears. Lowellin claims to be immortal. He claims to be the world’s only hope. But is he really? Or does he have other motives?