Minecraft wiki entry for Beginner%27s_guide, associated text: Progression beyond the Overworld is fairly limited: Eventually you can build a Nether portal to reach the Nether, where you can get materials for more complex crafting, the resources to brew potions, and the very top tier of tools and armor. The Nether materials also let you reach the End dimension, where you must defeat the Ender Dragon (the only mandatory boss); this unlocks the outer End Islands, where you can get an elytra that lets you fly, and shulker boxes for more storage. There are also two optional bosses: the Elder Guardians in the Overworld oceans, and the Wither, which is summoned with Nether materials.