Minecraft wiki entry for Nether_survival, associated text: Killing the various mobs that spawn there is tricky. Blazes, zombified piglins, and ghasts pose a threat, though wither skeletons are a minor annoyance. Mobs spawn at a faster rate in a nether fortress, and trying to kill all the zombified piglins is impractical, so it is best to just leave them alone, as a large pack of zombified piglins could knock you off into a lava ocean. A few of these mobs can be prevented from spawning at all with proper light levels. Blazes spawn at light level 11 and under and wither skeletons at 7 and other, so lighting up the entire area with torches is recommended. Ghasts need a large space to spawn, 5x4x5 blocks with a solid block beneath them, so light sources should prevent all those mobs exceptzombified piglins from spawning. The zombified piglins are neutral, so avoid accidentally hitting them and you'll be fine.