Notches Realm is the hardest realm to get into, and the hardest to get out of. It is the home to the herobrine boss.
How to get there
To get to Notches Realm, you must drink a Goblet Of Notch, which is the hardest objest To get in survival mode. The crafting recipe is a block of diamond, a block of gold, a block of iron, a grass block, a nether star, an end stone, a diamond sword, a diamond shovel and a diamond pickaxe. It will take any entity including mobs and players within ten blocks.
The Realm is about the size of the end, but the blocks it is made of are random blocks from the game. This includes chests, and although may require a little mineing, the contents of any chest spawned is random. The sky is white.
The Herobrine boss start off with the health of six withers. When you begin to fight him, he will be armed with a bow, and attack you. He will also, every three minutes, spawn waves of a random type of mob. All neutral mobs will see herobrine as an attack on their kind, and attack you. If you are lucky, you will get a few waves of passive mobs. If you are unlucky, you will get blazes, wither skeletons, endermen and ghasts. After the health of herobrine goes down to the heath of four withers, he will become yellow, and will stop moving. He will be invinsable in this state. Then, an enderdragon will spawn, which you will have to fight. After beating that, another one will spawn, but with skeletons and blazes rideing it. These will be invinsable until the dragon is dead. After this is beat, there will be a wither boss. Then, herobrine,goes back to his previous state, but will spawn no passive mobs, all creepers will be charged, all spiders will be jockeys and all mobs that can, will wear armour and hold equipment. After herobrine goes down to the health of two withers, he will grow to the size of a giant, and have a stone sword, where he will attack you. When he has the health of two zombies, he will shrink to regular size and punch you. When you kill him, the sky will turn to a montage of herobrines face. He also drops five of each block (diamond, lapis, gold, iron, coal, emerald and redstone), a Steve head and 100 levels if xp. 100 seconds later, a script will appear, with notch thanking you. Then the credits will play, and at the end, there will be a picture of herobrines face, with words saying 'dare you try again' and you will spawn at your spawn point.