Minecraft wiki entry for Nether_survival, associated text: The way to navigate through a nether fortress needs torches. When you finish a part of the nether fortress, put a torch at the entrance of the room to help you explore the nether fortress easily. Or you could block off the entrance with a certain block (like cobble). Wither skeletons can give you the Wither effect——a health draining status effect made by both a wither projectile or wither skeletons hitting you. Blazes are extremely dangerous and can be in the hallways and rooms, so make sure you are aware of that.