Turns biters into an overwhelming zombie horde. Enemies come in far larger numbers and are individually much weaker - a swarm to be mown down, not a handful of bullet-sponges. Your destroyed buildings become sources of new zombies, infection creeps through your factory along the flow of goods, and the dead don't always stay dead. This mod makes the early game a real challenge, and rewards that with endless fuel.
Mods introducing new content into the game.