Dark Sack is the main antagonist of the video game "LittleBigPlanet - Darkness Ahead".
He is the creator of the Negativitron, and once wreaked havoc on LittleBigPlanet long ago, but he was captured and thrown into the most secure jail ever: The Center of the Earth. Years later, he escapes when he finds a tunnel hidden in the dirt, and digs his way out, and wreaks havoc on LittleBigPlanet once again.
The first battle is on a grass platform, with burning wood beneath. He uses his robot to try to destroy you, but, eventually, he is defeated, and uses his head as a spaceship, and destroys the grass platform, launching everything into space.
The second time, you must hop across objects in order to get to the head. Eventually, he is destroyed. After that, everything goes back to normal, and Dark Sack is trapped inside the machine, in the dump.