Natrium Worm

The Natrium Worm was a type of multi-headed green worm that lived on pure sodium chloride. It lived under the sands in the dunes of Bruvoldaveer, on the outer reaches of the Galactic Salt Trail. Over many thousands of years the salts were mined and the worm, desperate for salt supplies, began to attack the salt traders for their cargo of salt. The Salt Trails developed a reputation for being cursed.

The Eleventh Doctor, (with Amy Pond and Rory Williams), managed to destroy one of the worms by luring it into a watering hole where the traders' salt cargo had been dumped. While Natrium Worms had the biology to absorb large quantities of salt their weakness was their biology’s inability to cope with other minerals (like water). The result was that the Worm exploded. (DWAM: The Salt Solution)