You have to defeat them before they evolve into stronger parasites. They come in 4 stages, the buglin, the infected mobs, and the fully evolved parasites. Mobs buglin - spawns in dark, evolves into rupter after a minute rupter - infects passive mobs evolves into a random beast after 2 minutes infected mobs - infects passive mobs evolves into a random beast after 2 minutes random beast (5 total) - powerful enemies that infect mobs and kill the player Weapons pickaxe - mines fast, craftable scythe - kills fast, gives speed, craftable bow - shoots projectiles that infect and kill mobs, craftable