Grimstone Dungeon

Grimstone Dungeon is a dungeon beneath Grimstone. It contains the Ancient Furnace, which can smelt cannonballs at double the usual speed; an ancient mould; and a fairy ring, code DLP. This fairy ring is only accessible once the player has moored on the island at least once.

Alongside these features, the dungeon is the only location where frost dragons reside, located in the centre of the dungeon. To the west of this area is another cave with frost dragons, though these can only be killed on a slayer task. Attempting to attack these dragons outside of a slayer task will result in the message "You feel a strange coldness wash over you, filling you with fear. You decide it best not to attack these dragons without permission."

They can be accessed either by climbing up the rock face from the north or south; the south climb requires 83 Agility, which can be boosted. Chilled jellies can also be found to the north and west of the fairy ring.

Attempting to set up a Dwarf multicannon anywhere in the dungeon will result in the message It's far too cold for you to set up a cannon here.

• Evidence of a certain shadow entity, most known for being associated with the fall of Imcandoria and the Lassar Undercity, appears to have been present in the dungeon at one point in time:
  • The ancient mould has an indent that resembles the Ancient Pillars found on Mos Le'Harmless and in the Lassar Undercity (though the Lassar pillar is much larger). Notably, the mould is described as being "unnaturally cold to the touch", a trait that black stone is said to possess in RuneScape 3, and having a blackstone fragment in the inventory gives additional dialogue.
  • The ancient furnace and the nearby pillars strongly resemble Imcando architecture (as seen in Camdozaal and Cam Torum). With two dwarven skeletons found nearby as well, this suggests the furnace was once operated by the Imcando prior to the fall of Imcandoria.
  • When wearing the ring of visibility or ring of shadows, shadowy hands can be seen emerging every 28 ticks from ripples in the water near the furnace and mould.
    • The Shadowy hands share the same model as the ones at The Nightmare