Worm That Walks
The Worm That Walks is a monster abstractly tied to the Cthulhu Mythos of Lovecraft. The idea was inspired by the end of his story, "The Festival", although readers have argued he may have been describing something more like a single giant maggot instead:
Wisely did Ibn Schacabac say, that happy is the tomb where no wizard hath lain, and happy the town at night whose wizards are all ashes. For it is of old rumour that the soul of the devil-bought hastes not from his charnel clay, but fats and instructs the very worm that gnaws; till out of corruption horrid life springs, and the dull scavengers of earth wax crafty to vex it and swell monstrous to plague it. Great holes secretly are digged where earth's pores ought to suffice, and things have learnt to walk that ought to crawl.
In a nutshell, the Worm that Walks is a horrible pseudo-undead monster consisting of a vast swarm of worms (or leeches, or centipedes, or other creepy-crawlies) possessed by the soul of a dead wizard, who directs the swarm as a singular body to continue its own existence. It was cemented in /tg/ culture by two Call of Cthulhu adventures; it takes its name from one adventure, likewise called "The Worm That Walks", but the monster now synonymous with that name appeared in a second adventure, "The Watchers of Easter Island", where it was called "The Crawling One".
In 4th edition, the Worm That Walks became an entire category of undead called "Larva Undead". The Larva Mage was the iconic "wizard made of worms", but it gained relatives in the form of the Larva Assassin (the soul of a Psycho for Hire given form through a swarm of hornets and centipedes), Larva Snipers (Cold Snipers (or at least sadistic marksmen) in life, now an undead archer composed of wasps) and Larva War Masters (General Rippers, Blood Knights and similar depraved, insane warriors in life, their souls called back and thrust into undeath as the Hive Mind of a swarm of carnivorous beetles).
- Slaugth - The 40k variant of the Worm that Walks.