Emorphous69
Refugee
Can you make the Division type of Ultra-Hard Hunters who are NPCs or zombies that are very difficult to kill and periodically come after you once a set of requirements are met? Requirements could be kill X zombies, and a mutant variant with different model, AI, attack, health, and of course, loot, would come for you. Furthermore, you could ■■■■ off a faction of NPCs (another idea) and they would send either their own personnel or hire a Hunter-like merc which is extremely lethal, and would require you to use more than just a couple of swings and a few bullets to defeat.