Rockworm

The Rockworms are the largest creatures on Planet U. They are massive worms that bore tunnels through rock. With powerful teeth and massive appetites, they seem to do nothing but sleep and dig. Their tunnels can stretch on for thousands of miles, twisting around. The Rockworm diet consists of anything they can bite into. Since they have no eyes, they can't see what they're eating, so they just eat everything. Like worms, they eat materials that they can grow from and excrete the remains, which is how Fertile biomes are created. Energy Crystals are important, obviously, since they provide energy and hold the massive beast together. Rockworms can grow up to 80 milks wide, the size of a one-block tunnel. In length, they are usually around 250-300 studs long, but have been found at sizes up to 600 studs. They are probably very old. If you see one in a level, move to an island. They will tunnel under your buildings and destroy them otherwise. The best method of defense against them is to RUN.