The Worms are not indigenous to Wet Planks. They migrated along the Tidal Pools from world-to-world. Normally these are not dangerous - in most places these worms simply manifest as earthworms. However, the isolating nature of Wet Planks has mutated these creatures over times. They've become aggressive, fractalized, forking creatures with multiple mouths - a hyper-aggressive ivy spreading across and eating their way into the foundations of the world.
The Tidal Pools that invite these creatures into Wet Planks form deep below the 30 Water gates that connect Wet Planks to other realms. They seem to feed and grow on gate radiance. One solution might be to close all the world's gates. But that would provoke other challenges for the people of Wet Planks.
Three groups are starting to see clues about the presence of a Usurper force:
- The Lumber Ships and Chipping Ships that visit the World Rim have noticed that the world's water level is decreasing
- Certain cultists in the Parliament of Hulks and the School of Ruddermen have heard of rumors from the Gill Men that the world is leaking away.
- Fishing boats are seeing evidence of large scale spontaneous fish kills in the areas near Water gates. That phenomenon is quite new; usually the areas around Water gates are teeming with marine life of all sorts.