Nightmare Mode is a new mode for Zombie Plague 4.3. That is edition of Plague mode and in this mode the 50% of the server are Assassins and 50% are Snipers. Assassin kills with one shot and Sniper kills with one shot. The map is dark too. On CS Forever Zombie Plague it looks like this:

COST: 5 EURO AMXX + SMA – BUY NOW