Error883

Hi, my name is Sasha! one day I decided with a friend to play minecraft version 1.16.5, I created a server on aternos, we went in and started playing, we played for 2-3 hours and my friend told me that he needed to go to bed, he left and I continued to play alone, after a while a certain error883 came to the server, I thought that my friend decided so to make fun of me, I started writing in the chat that stop trolling me because it's not funny. I tried to kill him, but I couldn't, as if he was in the creative, I remembered that my friend wasn't an admin and it clearly wasn't him, I started asking him: "who are you?" "what are you doing here?" but he didn't answer me, then I went for a walk around the world and started noticing various bugs chopped trees, mushrooms and met a black tree, then I went into the mine fell into lava and died I was reborn on spawn wanted to go to the village and saw that it was destroyed! I was shocked by this, but then not far from the village I saw a cross made of redstone blocks and a record player,there was a record 11 lying nearby, I decided to insert it into the player, the music started playing and the error883 with the inscription "LEAVE" started spamming, he started running after me, I got scared and started running away, I ran into the forest, but the chunk disappeared under me, I fell into it and the server crashed.... the name of the server has changed, but error883 and its description have changed to strange characters