The Extinction Campaign — Christian Warren Freed

Some men are destined for greatness. Most grind through life and are forgotten by the pages of history. But some men, they become the stuff of legend. Even legends go through Hell to discover their true selves. Aradias Kane was a child when he watched Berserkers kill his family. Vowing revenge, Kane became a Slayer: a nomadic order of men and women dedicated to removing the Berserker threat. Kane's adventures take him across the desert, gathering others to his cause. His actions become hurried upon learning the galactic Imperium has dispatched an assault division to Helscape. Instead of helping eradicate the Berserkers, the Imperium intends to capture them and use them in their war.
Nathan Bourne watches his future dwindle with each passing day. His wife left him and took his child and he has a dead end job in the local police force. He needs change but doesn't know where to turn. The choice is stolen from him the night his partner is murdered by a pack of Berserkers who have discovered a portal between worlds. Nathan chases them back to Helscape and becomes trapped between the Berserkers and soldiers of the Imperium. Only by teaming with Kane does he stand a chance of getting back to Earth.