Entity 1505

I was playing Minecraft. I was looking for disc 11 and disc 13. I went into the caves to get some diamonds. Then I accidentally mined into the deep dark. When I got in, the warden spawned and then immediately died. I looked around to see what it did; but saw nothing. When I turned around to back to the surface, entity 1505 said "hi" in the chat. After that, he said "1505 1505 1505 1505 1505 1505 1505 1505". Then he disappeared. When I got out of the cave, my house was completely burned down. When I went to mine a tree, once I mined one block, I turned around because my crafting table was still there. And once I made wooden planks, entity 1505 appeared right in front of me. And said: "I am the only one who could be in this Minecraft world." Then he killed me.