Ankheg

An ankheg looks like a gigantic worm with six legs, each tipped with a hook for digging and gripping. Its jaws are strong enough to bite a small tree in two. Hard brown or yellow plates armor everything but its soft pink underside. It has shiny black eyes, a small mouth set with rows of tiny chitin teeth, and two delicate antennae that pick up the movement of man-sized creatures as far as 300 feet away.

Its favorite tactic is to wait 5 to 10 feet underground until its antennae register footsteps, then tunnel straight up beneath the victim and catch it in its mandibles. The jaws crush for 3d6 each round while acidic juices add another 1d4 per round until nothing is left.

Once every six hours it can spit a stream of digestive acid up to 30 feet, dealing 8d4, or half with a successful save vs. poison. Because spitting leaves it unable to digest anything for the next six hours, it saves this for emergencies.

Ankhegs favor forests and good farmland, endlessly chewing twisting tunnels 30 to 40 feet down through rich soil. It sleeps, eats and hibernates in a widened chamber where a tunnel ends, and once a field or forest is hunted out it relocates. It keeps no hoard, but undissolved objects that fell from its jaws lie scattered through its tunnels.

They mate in autumn. The female then kills the male and lays 2d6 fertilized eggs in his corpse, and within a few weeks about 75% hatch and start eating. After a year the young look like adults and live on their own; they have 2 Hit Dice, AC 2 (AC 4 underneath), bite for 1d4 plus 1d4 acid, and spit for 4d4 to 30 feet. From then on each year brings full adult abilities and another Hit Die, up to 8.

Starting in its second year, an ankheg molts before winter: two days to shed, two weeks to grow new armor. Meanwhile it is sluggish and exposed, with AC 5 (AC 7 underneath), half speed, a 1d10 bite, and no spit. It hides deep in a tunnel and oozes a foul fluid that smells like rotting fruit. The stink keeps most animals away, but it also guides human hunters and starving predators right to it.

In cold lands ankhegs hibernate. Within a month of the first snow, one digs a den deep in the warm earth and lies dormant until spring, living on nutrients stored in its shell. It gives off no odor then, so it is hard to find, and its antennae still work. A disturbed sleeper is fully awake in 1d4 rounds and can then move and fight normally.

An ankheg can kill a farmer, yet it does his land good: its burrows let air and water into the soil, and its droppings enrich it. It will eat rotting matter in the ground but much prefers fresh meat, and only the fiercest predators bother it. Dried, cured shells make AC 2 armor, and its digestive fluid serves as ordinary acid.