Around the time Minecraft's structure was just being created, 2010, Indev, Infdev, Alpha, there were talks going around the small staff at Mojang at the time of including a major enemy in Minecraft, worse than spiders, worse than creepers, something that would truly challenge the player or terrify them. Something humanlike, but in the uncanny valley. This is where the project codenamed "Annihilation" came to be. Annihilation itself started out as a few useless zeroes hidden in the code of early Minecraft versions, both as an easter egg and as a future reference for where the developers would write code for the entity.
Work on Annihilation began mid-Beta Minecraft, where features really began pumping into the game. The skin for the entity was procedurally generated, much like a Minecraft world, using grayscale colors and shades of red. The skin that came out of this computation looked nothing like a human, yet was pasted onto the Steve model. At first, the entity was given the not-so-terrifying AI of a zombie, but over time, Mojang workers adapted the zombie AI into something more like the Enderman AI we see today, not terrifying but incredibly unnerving.
The entity was being distributed behind-the-scene in Minecraft versions now, but of course was not able to be spawned using any stock game feature (spawn eggs wouldn't exist until after beta and release 1.0). The only way the entity could spawn was if exactly 8 zeroes were entered as the seed. Annihilation could only spawn at a specific coordinate in this "zero world". Even I did not discover what that coordinate was.
As Beta progressed, and as Mojang began to write out the official story of Minecraft, as it would be in 1.0, the staff locked the code of Annihilation entirely while working on features such as The End and the dragon that inhabits it, saving the entity for a future post-release update. The main developer of Annihilation, my father, noticed that the complex Java code of Annihilation had reverted to just zeroes in it's place, yet the entity would still spawn in a zero world at it's coordinates as intended in a test environment.
Annihilation was left almost abandoned following the release of Minecraft, where Mojang took a little break themselves from Minecraft, knowing their game had finally reached it's moment. However, in the rush to release Minecraft at Minecon 2011, no one in the developing team found the bug in the code that allowed Annihilation to merge itself into the main branch of Minecraft's code, giving it access to every bit and byte of the game.
Upon returning to their desks at Mojang office, the Minecraft team noticed that the code of Minecraft, which was a specific number set at Release, had grown exponentially in their absence. My father took a peek at the code he had written, and noticed that Annihilation had completely overhauled it's own code, even extending it using Minecraft's procedural generation engine and grabbing bits from other AI's code. When he tried to edit this code, it would immediately revert to zeroes and cause an error in the environment, before going back to Java code once again.
There was no one to blame for Annihilation going out of their hands. The Mojang office had been locked with the room empty before Minecon. My father was commanded to cease work on Annihilation until further notice, only attempting to find ways to remove its code from the game. Mojang couldn't afford to release versions of Minecraft with Annihilation's unplanned release, so Jeb took a few steps to at least lock the code of Annihilation so that it couldn't be ran in a Minecraft environment.
To the Mojang staff's relief, they were able to release Minecraft 1.1, the update that added spawn eggs, without any code for an Annihilation spawn egg, furthering their retention of Annihilation from the public. One night, however, Notch himself discovered the lie that would cause my father to lose his job. According to my father, Annihilation had plugged itself into my father's Mojang user, and edited the code for it's name, changing it to zeroes, making it look like he was the one to attempt to bring Annihilation back. Notch would not take any bullshit, and fired my father, removing him from the Mojang staff.
I had become an avid player of the game my father contributed to, excited for whenever he would come home to play it with me or tell stories about what goes on at the Mojang office. However, the day he got fired, he came home, went to his room, and slammed the door shut. No matter how much I pleaded for him to come out, it felt like he was too humiliated to even look at his son's face.
On April 30th, 2012, a user whose name is still unknown posted about a Herobrine-like entity on the Minecraft forums. The OP post went like this:
"I had created a new Minecraft world on versions 1.2.5 on the peaceful difficulty, intending to immerse myself in the serenity of a Minecraft world void of the fear of deadly creatures. Spawning into the world, I found myself on an entirely flat chunk of grass, surrounded by chunks of cliffs and hills. Thinking this would make an interesting moment on a seed showcase, I hit F3 to view the seed, only to discover it was one zero. I recorded this fact anyway on Notepad, along with my system time at the world creation, 12:00 PM, April 30th, 2012 (Minecraft uses the system time for its world generation algorithm if no seed is manually inputted). There were convenient steps on a cliff chunk facing me, which I climbed up to the plateau above. As soon as my head passed the edge of the plateau, I noticed a gray figure sprint at superhuman speeds away from me, just catching a glimpse of it. Thinking it was a figment of my imagination, I continued forth.
My next sighting of the figure would be much later in the game. I prepared to venture back down my mine, in pursuit of diamonds. Oddly enough, the game had been crashing to 0 fps and, upon viewing the F3 menu, 0MB RAM usage every so often, which I thought was due to background processes on my computer which would subside soon enough. Even with the logical answer, I became nervous, my reflexes ready to snap at any button in front of me if something were to happen. And just as expected, I snapped my player's head towards my mine to find all torches missing, and the entity fading out at the bottom of the diagonal cavern. I hit print screen fast enough to capture the only evidence I have of its existence. Look at it, and look at it closely.
Following this sighting, my world began to exhibit quite strange behaviour. My strip mines at the bottom of the diagonal mine I sent would eventually begin crossing the same lava cavern over and over again, no matter how far I horizontally mined, same ores and everything. I would begin experiencing constant crashes, with the crash logs being entirely zeroes (no help obviously). I keep pushing my Minecraft's allocated RAM up, but still get huge lag spikes and RAM crashes."
Another interesting Entity Zero sighting was claimed later on, this time under the circumstances of being in a Feed the Beast world, and the entity actually interacting with the modded parts.
"I have basically reached the late-game in my FTB world, with a mass fabricator printing out valuables in absurd quantities, a full set of quantum armor, but still no completion of the game. Since this world's creation only a few weeks ago, nothing out of the ordinary has occurred. I spent probably the first two weeks of the world's existence depleting a sizable volume of the area of its natural resources, to jump-start whatever endeavors I would perform following. No, no Herobrine sightings or shit happened even during these lone nights mining away in deep caves. The following weeks would start with my attempts at comprehending what aspect of FTB to start with first, which ended up being IndustrialCraft 2, before using the fruit of my IC2 accomplishments to branch out to other areas and expand the base I was nurturing.
Up to this point, everything seemed normal, until the RAM crashes began. No crashes of the game, just the RAM usage suddenly dropping to zero every so often. I originally made no connections of this to something supernatural or paranormal or something, thinking it was just the many machines and gadgets working away at my PC and slowing it down. However, in an attempt to view the cause of this in the log files, I discovered at every timestamp at which a RAM crash occurred, all that would follow the timestamp would be a string of zeroes. No indication of the source of the problem whatsoever. I noticed that the output per day of my mass fabricator began to decrease too, despite my high voltage solar farm being unchanged and protected from all outside threats. Upon further inspection, I discovered that someone had detached many glass fiber cables, rendering half the solar panels useless. No mob or in-game feature could cause the cables to disappear otherwise.
Things only became stranger when I returned to the mines after a very long time to collect resources to replace the cabling and for more advanced technology. Old strip mines that I swore went through nothing before began passing through the same cave over and over again upon extending them. I could even swear that I saw a grey, transparent figure darting past the corners of my vision at times. The creepiest experience in this exploration was when I mined through a tunnel straight to a completely empty chunk, with the exception of a bedrock layer at Y=0.
Returning to the surface at night, and coming back to my base, I caught the gray figure again next to my mass fabricator, before it modified the facing of multiple machines with a bare hand, causing the entire base to blow up due to voltage differences. I survived the explosion, however still cursing the entire time.
In the process of rebuilding the technological empire I had established, I would continue to spot my machines modifying themselves, as well as the even stranger occurrence of mobs and their AI completely freezing, causing them to face north and cease to interact with the environment, even if I punched a hostile one. Entrances to my mines closed themselves off with obsidian seemingly placed by someone. Every time I wasn't keeping an eye on a certain aspect of my world, it changed or completely disappeared."