The Grotesque is a hideous manifestation of the evil beneath Lumbridge Swamp, and it is also the reason for the swamp's tainted appearance. Its hands, and occasionally its body, emerge at The Nexus in the swamp, while its hands can always be found as wall beasts in the Lumbridge Swamp Caves. If the streams in the Nexus are arranged correctly 5 to 8 times in a row, it will appear for a few seconds allowing it to be clicked on to banish it, rewarding grotesque bones which when buried, grant Prayer experience. When the experience cap of the nexus is met, the Grotesque and its arms will disappear, leaving behind an empty crater, although its arms inside the swamp caves will remain.

The priest Augrum came to Lumbridge Swamp to study the Grotesque. Satisfied that the Grotesque could not grow any bigger and so wasn't a threat, he left his apprentice Ysondria to guard the area. However, the Grotesque continued to grow, so Augrum sought aid from druids, who brought the four pillars used to contain the Grotesque.

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