The massive burrowing monster known as the purple worm terrorizes the creatures of the Underdark as it chews through solid rock in pursuit of prey. A dim-witted, ravenous force of nature, this creature regards anything it encounters as food.

Loud noise attracts purple worms, which have been known to interrupt underground battles and tear through subterranean cities seeking prey. The underground civilizations of the drow, the duergar, and the mind flayers maintain special wards around their settlements to deter these monsters. Though most common in the Underdark, purple worms are frequently seen on the surface world in rocky and mountainous lands. The maw of a purple worm is large enough to swallow a horse whole, and no creature is safe from its hunger. It lunges forward by rhythmically compressing and expanding its body, catching other Underdark dwellers by surprise with the speed of its advance.

When a purple worm burrows through the ground, it consumes earth and rock, which it breaks down and constantly excretes. Precious metals and gems can thus be found within the bodies of purple worms, which are targeted by particularly brave and foolhardy treasure hunters. A burrowing purple worm constantly creates new tunnels throughout the Underdark, which are quickly made use of by other creatures as corridors and highways. Because a purple worm rarely returns to its own tunnels, such passageways are a good place to avoid these monsters. Areas rich in prey quickly become interlaced with complex tunnel systems resulting from several worms hunting together.