Monster Analysis: Purple Worm and Frost Worm

Purple Worm

  • First Appearance: 39 Omens
  • Armor Class 18
  • Speed 50 ft, Burrow 30 ft (15 ft through solid rock)
  • Blindsight 30 ft, Tremorsense 60 ft, Passive 9
  • Average, Max HP: 247, 390
  • 283 taken, 21 HDYWTDT by Percy (with L’il Sparky)

The purple worm is a gargantuan monstrosity, a ravenous hunter who detects its prey by the vibrations they generate, chewing through solid rock in pursuit. Smooth tunnels are the result of its travels, often used by denizens of the rocky mountains or Underdark where it lurks. Its toothy maw is large enough to swallow even large creatures whole. Creatures it cannot bite also may be a victim of its poisonous stinger.

Adventurers who are trapped inside the worm take 6d6 of acid damage at the start of the creature’s turn. They can be regurgitated to safety if they deal 30 or more damage on their turn from inside, provided the worm fails its Con Save (DC 21, with a Con mod of +6).

Frost Worm

  • First Appearance: 39 Omens
  • Armor Class 18
  • Speed 50 ft, Burrow 30 ft
  • Blindsight 30 ft, Tremorsense 60 ft, Passive 9
  • Average, Max HP: 168, 240
  • 324 taken, 87 HDYWTDT by Grog 

The frost worm’s roots appear to stem from Pathfinder (at the very least, that’s where the mini came from). However it has been modified to be a significantly easier encounter, much more in line with its purple cousin. The worm’s frost breath dealt a 30-foot cone of cold damage (at 33 and 36, we estimate 8d6). The versions of the frost worm we came across also had an ability to erupt in a blast of cold upon its defeat; we consider Vox Machina very fortunate that this effect was absent.

The Encounter

The most dangerous capability of both worms were their appetite. With the high damage requirement to escape from inside and an even higher constitution in case that requirement is met, the quickest option to escape the extremely acidic innards was magic (e.g., Dimension Door) or killing it outright.

The most notable wrinkle in the fight came from the miscommunication of Wind Walk. (We did confirm during the live stream that both the Android and iPhone spell sheet apps listed the spell as requiring 1 action to cast, while the PHB does specify it takes a full minute. Let that be a warning to confirm consistency with your own resources!) With half the party unable to provide support and the other half quickly becoming a meal, the difficulty of the encounter was notably increased. Fortunately, D&D is a flexible game with a malleable reality, so with a little creative thinking, the battle was evened once more in time for the stranded members to receive appropriate assistance.

Another note to DMs: if, at any point, the party has the opportunity to become richer than sin, keep in mind to always have a better reason for them not to. A collapsing cavern, a bigger version of what just almost killed the party, the threat of losing access to something even more important…