Herobrine was the brother of Notch the Creator. The two created the world together, creating the villagers and the adventurers. The two groups would work together to create a civilization. Notch would create other worlds while Herobrine guarded Earth.
At least, that was the idea.
Herobrine always hated that the beings had free will, and that they could make mistakes. He wanted perfection, but if you have free will, you can change your mind, and if perfection changes it must then be imperfect. He attempted to destroy the villagers, and then created a plague that would infest dead bodies with the power of zombification, taking their freedom and making them Herobrine's pawns. Then Notch returned.
Notch attempted to convince Herobrine that this was the wrong way to create harmony, and that this race didn't need perfection. Herobrine wouldn't listen, however, and attacked Notch. The two had a battle that, because neither needed sustenance, lasted for days. Eventually, it was obvious that Herobrine's power was beaten. Notch could not kill him, as there will always be evil to sustain the Dark One, but he could banish him. Herobrine was banished to an area that was even below the Nether. Notch never suspected how powerful Herobrine was becoming...
Herobrine will slowly show signs of existence.
Herobrine will spawn large buildings with a giant "Darkkon Incorporated" sign after 7 minecraft days. When you walk in, there will be complimentary food and potions, but don't get too excited; these are actually retextured potions of Blindness I and Nausea I (3:00). Even though there is glowstone, hostile mobs will still spawn, except for Endermen. Undead will spawn most often, and on Hard they will give Wither I (Wither II for Wither Skeletons). Although there are stairs to the top, there is nothing at the top but 5 (yes, 5) monster spawners in a 15x15 area. However, there will be a pressure plate on the bottom floor revealing a hidden stairway. Walk down this to face an Avatar of Herobrine.
Avatar of HerobrineEdit
This avatar has 80 health, deals 5 damage, and will teleport. Also, he can inflict Wither, Blindness, and Nausea II by touching you. He will also spawn Zombies as if he is a monster spawner. When you kill him, he will rise up into the air, and there will be an area of darkness around him as he slowly disintegrates (think mutant enderman here). He drops a Talisman of Herobrine, meaning that undead will not attack you while it is in your inventory.
There will be a chance for undead, after 10 minecraft days, to be immune to Smite, and to have 40 HP and strength I.
After 14 minecraft days, Dark Towers will spawn. These towers have witches in them. At the top of the tower, there will be a Priestlord of Herobrine, with 80 health, and the ability to combine his potion effects. He will also buff himself and float one block above the ground. While fighting him, witches will appear to protect him. The Priestlord will drop nether stuff, and rarely a Witch's Hat. Witches won't attack you with this hat on (although Priestlords will still know you're not a witch), and potions you use have double effect. The hat has infinite durability, but does not give armor.