The Nether and The End

A Nether portal is a rectangular obsidian frame, at minimum 4 blocks wide by 5 tall (a 2-by-3 interior opening), and at maximum 23 by 23. The four corner blocks aren't required for it to activate, even though naturally generated portals always include them. Obsidian itself needs a diamond or netherite pickaxe to actually drop when mined. Once the frame is up, setting the empty interior on fire — with flint and steel, a fire charge, lava next to a flammable block, or even a ghast fireball — fills it with swirling purple portal blocks.

Horizontal distance compresses by a factor of 8 between the two dimensions: moving 1 block in the Nether covers the same ground as moving 8 blocks in the Overworld, while your Y coordinate stays exactly the same in both. Step into a portal and the game takes your X and Z, divides them by 8 (or multiplies by 8 going the other way), and searches near that converted point for an existing portal before creating a brand new one. Two Overworld portals built close enough together can end up converting to nearby enough Nether coordinates that they link to the very same portal, which is the usual cause of "why did I end up somewhere I didn't expect."

Beyond its mobs, the Nether itself is a hazard. It's built almost entirely from netherrack, soul sand and basalt over seas of lava that are far more common than any water — and water doesn't behave normally there anyway, since a bucket of water simply evaporates on contact with most Nether blocks. Beds and boats explode instead of functioning at all. The biomes vary sharply too: Nether wastes and soul sand valleys are relatively open, crimson and warped forests are dense with fungus growths, and basalt deltas are jagged, cramped, and especially lava-heavy.

Piglins stay neutral toward you as long as you're wearing at least one piece of gold armor; take it all off and every nearby piglin turns hostile. Even in gold armor, though, you can provoke them: attacking one, breaking gold-related blocks nearby, or opening or breaking any chest all trigger hostility, and an attacked piglin calls in others from a good distance away. Offer a piglin a gold ingot, by right-clicking it or dropping the ingot nearby, while it isn't angered, and it barters, tossing back a random item after a several-second pause. A piglin that ends up in the Overworld or the End turns into a zombified piglin after about 15 seconds.

Ghasts are the large floating mobs that shoot explosive fireballs from a distance, mostly over open Nether wastes and lava seas. A well-timed hit on an incoming fireball, with a sword swing or an arrow, knocks it right back toward whatever fired it, which is the standard way to damage or kill a ghast without ever closing the distance. Nether fortresses are the tall brick structures where blazes spawn, the only source of blaze rods, which craft into blaze powder, the key ingredient in both eyes of ender and brewing stands. Wither skeletons also spawn there, dropping the skulls used to summon the Wither later on.

General Nether survival matters here too: since it's built mostly from netherrack, soul sand and basalt over huge lava seas, staying off unstable ledges and building safety rails around any drop matters even more than in the Overworld. Bringing blocks to bridge over lava is worth it, since falling in is far more common here than accidentally mining into a lava pool back home. Fire resistance potions make both lava crossings and ghast fireballs far less dangerous, and are worth brewing before any serious trip, especially one aimed at a fortress.

An eye of ender is crafted from an ender pearl (dropped by killing endermen) and blaze powder (crafted from a blaze rod, itself only available from Nether fortress blazes). Thrown into the air, it drifts in the direction of the nearest stronghold before dropping, and sometimes breaking instead of landing safely. Repeating this, walking toward wherever it lands each time, guides you to a stronghold buried underground. Once an eye starts dropping nearly straight down instead of drifting sideways, you're right on top of it, and it's time to start digging.

A stronghold's portal room holds 12 end portal frame blocks arranged in a 3x3 square shape with the four corners left empty. Each of those 12 frames has roughly a 10% independent chance of already holding an eye of ender when you find it, so a handful are commonly already filled, though it's entirely possible to find one with none. Fill every remaining empty frame with an eye of ender and the center fills in with a swirling black-and-purple void, the activated End portal. It's worth bringing a few spare eyes beyond the twelve you might need, since each throw carries a real chance of breaking instead of placing.

Stepping through the activated portal drops you straight into the fight with the Ender Dragon. The dragon roams among tall obsidian pillars, each topped with an end crystal (two or three of which are protected inside iron bar cages) that continuously heals the dragon back up whenever it flies close. Attacking the dragon directly while those crystals still stand is largely wasted effort, since the healing easily outpaces the damage most players can land. Destroying every crystal first, usually by shooting them from a distance, is what actually lets a fight against the dragon's health make real progress. Once the dragon is defeated, a portal called an End gateway opens nearby, leading to the scattered outer islands of the End, where End cities, tall structures built from purpur blocks, sometimes hold an End ship carrying the one item that makes exploring those islands far easier: elytra, for gliding.