Metalmaster

The metalmaster, also called the sword slug, is a big, leathery slug, usually dull purple to rusty red and rarely smoky gray or black. Its mouth is full of large serrated teeth able to bite through metal. It can repeat sounds it has heard and uses them to lure prey, though being dim it often picks the wrong noise for the moment.

At will the slug projects a strong magnetic field out to 30 feet (60 feet when acting on a field that is already there). Enchanted and plain metal respond equally but ignores ore and traces of metal in rock. Each round it can attract or repel, and at the end of the round it can stop or reverse instantly.

When attracting, it yanks small loose metal objects toward itself at 20 feet per round; small here means less than a sword or medium shield in size, and small fastened items come loose if their fastenings fail a save vs. crushing blow. Larger loose objects slide 5-10 feet per round, while larger fastened ones, or anything as heavy as a big anvil or metal throne, will not budge. Magically held items stay put, and barriers like wall of force stop the flying metal.

When repelling, it turns aside any missile with metal in it. Each round, anyone in metal armor is pushed back at least 10 feet unless a Strength check succeeds; those merely carrying metal weapons, coins or buckles also check, with a bonus set by the DM. Held metal items suffer -4 to hit while repelled, and the holder must make a Strength check or lose the item.

Pulled metal never hits the slug; it orbits instead, filling the area from 10 to 30 feet around it with a spinning hurricane of debris like a blade barrier. Creatures without magical protection take 4d6 per round there, or 2d6 with a successful Dexterity check. The field itself does no damage but often makes weapons strike the wrong target. Blink, jump and the like cannot dodge it and it extends into the Ethereal Plane, but teleporting out with dimension door or similar magic works.

Its teeth can shear armor but do not otherwise damage metal; it never eats metal, though any it swallows by accident does it no harm. It climbs steep slopes but not sheer walls or smooth inclines, has 90-foot infravision, and can feel roughly where any chunk of metal the size of a fist or bigger lies within 40 feet. Well fed, it regains 1 hp per turn, and a lost eyestalk may grow back in a day or two.

Metalmasters may pass the century mark. Mostly solitary, they team up to hunt in dangerous places and mate in deep tunnels or muddy bogs where they are unlikely to be disturbed. They like narrow tunnels close to metal and often lurk near metal treasure hoards, which both lure prey and supply ammunition.

Their favorite meals are big and red-blooded, livestock or grown humans, though hunger will make them eat almost any creature, living or dead. Their flesh is so bitter that only scavengers touch it, and so far alchemists and mages have found no use for its ichor or meat.