I know these have been suggested before, but I havn't seen a thread in a while. Hp: 50 for each segment and 10 extra for the head. Damage: 20 if hit by the body, and 25 if hit by the head. Spawning: lvl 3 planets or higher. 20% spawn rate. spawns 100 meters below surface, and grows every more 100 meters down (If it's not too much coding) Moves rapidly through blocks, and loses momentum when going through open space. Giant worms appear after about 1000 meters down, that create 3-block holes as they move. Drops:regular drops (pixels, leather, meat, etc) and giant worms have a 5% to drop a worm tooth. A worm Tooth has a swing rate of 0.50, but does 75 dmg.
Such creatures would have to be able to grip the background, otherwise they'd be highly vulnerable to ending up at the bottom of a pit of their own making. Plus, they'd have to store the material they chew through so that they don't completely ruin ore deposits and the like. Other than a few concerns like that, though, I could see this working.
