The Mewlips were a strange and secretive race, known only from a reference in a poem of the Hobbits of the Shire. Their identity is mysterious and indeed they may not exist at all; or they may represent a distant folk-memory of the Hobbits. They were said to be dangerous creatures, dwelling in the dark and feasting on unwary travellers who sought them out.
The Mewlips's dwelling place was said to be a dark valley far over the Merlock Mountains, through 'spider-shadows' and a forbidding wood, and beyond the marsh of Tode. They live and hide in damp, moonless and sunless cellars, where they sit and count their gold.
Behind the ScenesEdit
Though these geographical names are not otherwise known, they fit well with the long journey from the Shire across the Misty Mountains and through Mirkwood (which had marshland on its eastern fringes). If that assumption is accurate, the Mewlips' valley would have been in the east, probably somewhere in the region between the River Running and Redwater. Though in many instances it is said they live in an area with "cellars", the only known place in that location with a description like that is Dol Guldur.
John Rateliff suggests in the The History of The Hobbit that this poem may be related to the Long Marshes and that Dwarves and Hobbit may have ended up running into unpleasantness there and visiting the mewlips, and further disaster there. Many a rider and wanderer were lost if they had tried to find their way across the the marshes. The rather ominous line about rafts, men (i.e., raft-elves), and beasts disappearing in the Long Marshes suggests that Tolkien had some adventure in mind for what unpleasantness would have befallen the hobbit and his companions had they found their way into the marshes...We do, however, have a description of sinister cannibalistic monsters lurking in a swamp in another of Tolkien's works: his poem ‘The Mewlips’ (ATB poem #9).1 Given the degree to which Tolkien borrowed freely from his earlier works when writing The Hobbit – what I have elsewhere called his knack for autoplagiarism – it would be entirely in keeping for him to have done the same here, but in the event the story took a different direction and Bilbo luckily avoided having to slog through the marshes entirely."