Unidentified Entity

So, when I was playing Minecraft and venturing the Far lands, I saw a strange entity in the distance. It appeared to be corrupted, It didn't make any noises other than deep breathing. 5 seconds later, I heard one of the Cave sounds and the entity suddenly disappeared.

I was traumatized for a second, I went closer to where it was. It did appear again, but far away. this time its appearance was a little different. Some of the details were gone. I thought this was really strange, since any basic mob appearance doesn't ever change. Some mobs appearances do change. So it didn't feel too strange, but I thought it was a corrupted pig. I went after it, but it went deeper into the Far Lands. my hearts began decreasing slowly. they did stop at half-a-heart. what? Yeah. It was very creepy. Yes, It did disappear once the poison stopped. I didn't see it until 5 minutes later. It made a really loud noise and popped up right in my face. I turned it off quickly. That was so loud it almost blew my ears off. I wasn't even expecting it.

...

Once I turned the computer on, I logged in and Minecraft was still open full screen.

I was dead, but the screen didn't say "Game over" or "You died" It said "You will die soon"

I was scared. I respawned in a strange black void. Not the actual bottom void. but a room. I couldn't see a room, but I assumed I was in a room. I couldn't see the walls. I typed the command known as /kill which kills you, It didn't kill me though. It said "Don't you think you've caused enough trouble?" What the hell!?! I was stuck on edge and dread was building. and yes I was in a dark room playing this game? I typed the command again. but then a message box popped up: "Join us?" I pressed No, the screen faded to black instead of closing the message box. The message box was replaced with another message box? "REALLy?" I pressed "YES". My computer crashed. I couldn't turn it on for 5 weeks straight. I have resorted to using my laptop as my main computer ever since.