The Caverns Symbol of Ptolus City by the Spire

Chapter 22 The Caverns Cover Ptolus City By The Spire Drow Spider Underdark Red Eyes

Before Dwarvenhearth, before the Banewarrens, before the Spire itself rose from the ground, the area beneath what is now the city of Ptolus was honeycombed with natural caverns, created by the
flowing water of extensive subterranean rivers toward the sea.

These caverns lie far deeper below the ground than Ghul’s Labyrinth, the Undercity, and the sewers. Many creatures make the caverns their home, including dark elves, rhodintor, underground-dwelling locathahs, dwarves, and evil nagas of all types. And in the darkest levels of all, the Galchutt lie sleeping.

Caverns Guide

  • Giant’s Staircase/Eternity Cave
    • Umbral Lake, Kaled Del, and tunnels to the surface and Dwarvenhearth.
  • Serpent Caves
    • Mazelike caverns of the Children of Mrathrach: evil nagas of all kinds who worship Father Claw.
  • Locathah Cavern
    • Vast cave called Glaugsgulgus with shrine to the Sea Mother as well as to the God of the Open Sea and the Lord of Caverns.
  • Vaults of the Rhodintor
    • Great collections of chaositech items, both sleeping and meditating rhodintor.
  • Caverns of the Galchutt
    • Kastralathakasal, Throne of Darkness, and the Dreaming Stone.
  • Dark Elf Caverns
    • Ul-Drakkan and Ul-Sinistar fortresses, city of Nluguran, and Dreta Phantas.

Running the Caverns

Running adventures in natural caverns can be tricky, because it’s easy to think of them as being just like dungeons but with uneven walls. But everything about natural caves is uneven—the floor and the ceiling as well as the walls. Sometimes Balance checks (usually DC 15) are required in certain caves if characters are doing anything other than moving through slowly; the “floor” might be just a series of rounded boulders of varying heights or slabs of stone cast about at differing angles, often slick with dampness and slime.

The most straightforward way to get to the caverns is via the Giant’s Staircase, though entrances also link up in many places throughout Ghul’s Labyrinth. It’s hard to know exactly where one type of Dungeon area stops and the caverns start— many delvers find themselves in the caverns accidentally after passing through a mysterious hole in a sewer tunnel wall or down a channel from the Labyrinth. Other adventurers might venture here purposely in response to specific adventure hooks tied to one of the cavern areas discussed later in this chapter.

This chapter details some of the more infamous locations in the caverns, starting with the ones closest to the surface and ending with the deepest, most remote locales. Unlike the locations you’ve read in earlier chapters, most of these caverns are not individual encounter areas but entirely new adventure locations for you to expand upon, according to the specifics of your campaign. For a guide to the format of the descriptions and the icons used in the sections that follow, please see “District Neighborhoods/Locations” in Chapter 7: City by the Spire (page 168).

DM Tips

A passage from the lower levels of the Temple of the Ebon Hand (see page 379) leads into the natural caverns and provides access to the secret underground bases and temples of other chaos cults.

Random Encounters

DMs should use the caverns deep below Ptolus as an opportunity to stage encounters with unintelligent, unorganized monsters simply prowling for a meal. In the caverns, you don’t have to worry about whether the manticore can open doors or deal with traps, because doors and traps are extremely rare.

Although the kinds of subterranean encounters you can have are nearly endless, use this list if you need to generate an encounter quickly:

01-50No encounter
51-55Slippery rocks near dangerous fall (Balance check, DC 15, or fall 1d3 × 10 feet)
56-57Cave-in (see DMG)
58-602d6 dire bats
61-641d3 bat swarms
65-661d3 large monstrous spiders
67-681 grey ooze
69-70 1 ochre jelly
711d4 ogres
721d3 rust monsters
732d6 grimlocks
741d4+1 subterranean locathahs
751d2 cloakers
761 delver
771d2 basilisks
781 behir
791 athach
801d4 ankhegs
81-821d4 trolls
831 medusa
841d3 manticores
851 gorgon
861 chimera
87-881d4 stone giants
891 black pudding
90-911d3 grey renders
921 zaug
931 D'Stradi annihilator
94-951d4+2 adventurers (levels 3d4, random race)
96-981d4+2 dwarves (warriors levels 3d4)
99-001d4+2 dark elves (warriors with 1 male wizard level 3d4 and 1 female cleric level 3d4+1)

DM Tips

Very few troglodytes live in the area beneath Ptolus, so despite the fact that they are a common subterranean monster in the game, you won’t find them on this encounter list.

At the very bottom of the Giant’s Staircase lies a small ruined tower, standing watch at the entrance of the Eternity Cave. This tower, built by the dwarves, now stands empty.

As you expand on these caverns for use in your own Ptolus Campaign, remember to scatter Pits of Insanity throughout the areas, as described in Chapter 19: What’s Down There? (see page 416).