Rock Worms

Large worms, up to 50 feet long, that eat stone and metal. Rock worms can only be found underground, typically in rocky areas. They are very fond of limestone and granite. For the largest of these worms, eating a humanoid or other creature that happens to be in the way will be almost instantaneous, killing the poor person in quick form. (Causes 5d10 damage per round).
Smaller worms will attack and wrap around anyone in full armour, like a snake, smothering them with a strength of 35. Every round that the person does not make a strength test of 35 or higher they will be damaged for the difference between 35 and their result. The person will need a strength test of 42 to break free. The trapped person also cannot breathe while trapped.  [Note: a character can only hold their breath for 30 plus 2 times constitution seconds.]
Size: 150 to 300 Strength = size minus 1d10 MP = 0 Agility = 8 to 15 (7 plus 1d8)
Skin deflect 2d10. Bite roll does either size/10 damage (50% chance) or half of that (50%)