John Steakley

The planet is called Banshee. The air is unbreathable, the water is poisonous. It is home to the most implacable enemies that humanity, in all its interstellar expansion, has ever encountered. Body armor has been devised for the commando forces that are to be dropped on Banshee--the culmination of ten thousand years of the armorers' craft. A trooper in this armor is a one-man, atomic powered battle fortress. But he will have to fight a nearly endless...

Jack Crow is the leader of a team of mercenary vampire slayers dedicated to doing everything humanly possible to prevent Valek, the leader of the undead, from discovering the Berziers Cross, the only thing that can grant all vampires the omnipotent power to walk in the daylight.