The Worm of the World's End is a big worm. Seriously. I mean, we're talking really big here. Not just a tad bigger than something you're likely to find in a flowerbed and scare your kid sister with. It's actually the size of your average mountain range (!!!). Yes, that's right... it's that big.
Conceptually, the Worm of the World's End is the lovey-dovey-wrigglycuddle by-product of Jörmungandr and Níðhöggr, or at least a melding of the two in the author’s Norse mythology-fawning imagination. Demonstrating even more clearly that the author undoubtedly owns a papier maché battleaxe and an imitation Viking helmet with plastic horns is the fact that the Worm of the World's End spends most of its time slumbering under the roots of the One Tree. In exactly similar manner in Nordic mythology, Níðhöggr also makes its home amongst the roots of Yggdrasil, the vast tree that supports the nine realms of the Norse cosmos. Unlike Wormy however, Níðhöggr nibbles the afore-mentioned's roots - can you even imagine the size of the slug pellets that would be necessary to prevent further damage? One can only hope that there's a large well-stocked garden centre in Asgard.
Whatever the ur-idea, Jörmungandr’s other name - Midgarðsormr - translates as “Middle-Earth Worm” (do observe that vital hyphen, lest it become “Middle Earthworm”, which would be just plain embarrassing.), which is but a step to a more landborne direction.
The Worm of the World's End slumbers beneath the Earth’s surface, curled into itself as if over-enthusiastic about the concept of ouroborism. It'd obviously be rather liable to ruin one's (and everybody else's) day if such a creature were to wake and start throwing its weight around. Fortunately, Wormy can only be awakened either by an over-eager use of wild magic stemming from white gold, or by a drastic perversion of the Earth’s laws. Hence, “rousing the worm” in Landish talk denotes something rather more unpleasant than getting one’s manly sword to grow too long for easy use.
The Worm of the World's End's favourite snack consists of Elohim. It views these eldritch faery folk in much the same way as a chunky mid-Westerner would view a bargain bucketful of chicken nuggets... once roused from its soporific torpor, it just can't stop itself from munching on them. (As an aside, it should be noted that many others would be equally incapable of stopping themselves from munching on Infelice, the queen of the Elohim, but that'd be in a completely different manner).
Anyhow, if for some reason thwarted from accessing any more tasty Elohim, the Worm of the World's End will settle for chugging back vast quantities of Earthblood, a thing which will have the unfortunate side-effect of causing the world to be destroyed, unless of course there's an unlikely heroic trio comprising an embittered leper, a blubbing whiner and a shroom-crazed teenager around to save the day. Again there are clear parallels here with clinically obese mid-Westerners who, once they've eaten all the available stock within their local branch of McDonalds, will invariably turn to ordering as many triple-thick shakes as they can slurp down.
Aversions & Vulnerabilities
Despite its being an entity of both immense size and puissance, the Worm of the World's End has an inexplicable repugnance of aerial rhythmic gymnastics. It has been known on at least one occasion to shy away from a small band of Ur-viles and waynhim performing the macarena whilst improbably hanging from the tentacles of the large octopoidal creature known as Horrim Carabal, the Lurker.
Also, once sated by having drunk too much Earthblood - and that's a whole helluva lot of Earthblood, because Wormy is absolutely not a cheap date - the Worm of the World's End is bizarrely susceptible to being sung back to sleep by the massed voices of the Elohim Gospel Choir.