Minecraft wiki entry for Advancement_guide, associated text: Kill every type of hostile mob, and you only need to kill it once. Killing a type of hostile mob in your current world will be saved in the progress bar of this advancement. The 34 mobs you will need to kill include: blazes, cave spiders, creepers, drowned, elder guardians, ender dragons, endermen, endermites, evokers, ghasts, guardians, hoglins, husks, magma cubes, phantoms, piglins, piglin brutes, pillagers, ravagers, shulkers, silverfish, skeletons, slimes, spiders, strays, vexes, vindicators, witches, withers, wither skeletons, zoglins, zombies, zombified piglins, and zombie villagers.