There is a hidden entity. Not a mob. An observer . After 500 block breaks, a new block type appears: . When you break it, it doesn't drop items. It drops a reflection of you—a perfect clone with your exact gear, your exact hunger, your exact fear. It doesn't attack. It just mines the block you're standing on .
But the clone remains on your old island. And now, in the distance, you see a second mirror block forming on its feet.
It stands up. It mines its own block.
And when it does, the block doesn't respawn for a full 60 seconds.