Lovely, eh? It's a land planarian: a species of flatworm with a serious agenda for world domination. Originating in Asia, it is now spreading through the Americas and Europe, leaving a trail of dying earthworms in its wake. So what's a DM to do? Stat up a giant one, of course:
Giant Land Planarian
Slithering through thick forest topsoil, this blind, predatory, hammerhead worm searches endlessly for human or animal flesh. Completely blind, it operates by scent alone.
The Giant Land Planarian can reach up to 12-18' in length as an adult. It attacks by winding itself around its victim, covering it in thick mucus, before inserting its tube-like mouth into the unfortunate's body and sucking it dry.
The monster's most impressive trick is its ability to regenerate. It automatically recovers hit points at the rate of one per turn, and can only be properly destroyed by fire or acid. On a successful critical hit with a slashing weapon, the body will break at the point of attack. Parts of the body that are severed immediately begin to grow into new individuals; the creature's remaining hit points should be shared between the two portions according to length. New individuals regenerate at the same rate as the main body; by the time they have gained 10 more hit points they have grown a new head and a new mouth with which to feed.
The creature has no eyes or ears and operates by an exceptionally keen sense of smell, so it is never surprised.
Giant Land Planarian
Climate/Terrain: Temperate and subtropical forests
Activity Cycle: Any, usually nocturnal
Intelligence: Nil (0)
Alignment: None (Neutral)
No. Appearing: 1
HD: 6+6 - 9+9 (depending on length)
THACo: 14 - 11
No. of Attacks: 1
Special Attacks: The Land Planarian attacks by constricting its foes and sucking them dry. On a successful hit roll, the creature causes no damage, but immediately rolls again to hit. If the second roll succeeds, it can entwine itself in its victim and begin to feed. It drains the blood and organs from its target at a rate of 8 hp per turn through its tube-like mouth. The creature will not relinquish its hold unless it has lost 90% of its hit points or it is confronted by fire.
Special Defences: See above. The Land Planarian suffers only half damage from bludgeoning and piercing weapons. It takes double damage from fire.