This article assumes the PCs enter the cave from the west side of the cavern. If they do not, modify the encounters to suit your needs. Level 1 Cavern, Part 2 describes most of what remains of the large cavern on level one of Undermountain. The article following this one will describe the other parts of the cavern and rooms that lie beyond. As the PCs enter each area, use the read-aloud text for that area.
This cave developed a strange ecosystem due to Halaster's husbandry. Small insects flit about or crawl on the ground, providing food for thousands of bats that periodically leave the cavern to fly about Undermountain before returning en masse. These bats create waste that helps to form earth in which the glowing mushrooms and other fungus grow. The cavern's fungus forest provides food for giant fire beetles, which in turn provide food for some of the cavern's other inhabitants. The monsters described in the area descriptions below exist largely outside this ecosystem, leaving the cavern to hunt for larger and better-tasting meals than fire beetles.
As the PCs explore the cavern, describe the features they encounter. The area descriptions below offer more details. If you'd like to have the PCs encounter creatures other than those listed in the area encounters, consider the monsters listed in the Other Cavern Inhabitants sidebar. The many small side caverns not given any particular detail in this article make good places to encounter such creatures in their lairs.
Fungus Forest: The map depicts several areas of fungus forest growth. These squares are difficult terrain. The large mushrooms block passage. They have a hardness of 6 and 480 hit points, and each is about 5 feet tall and 4 feet thick. These large blue mushrooms glow with a dim radiance and release a sparkling cloud of spores when disturbed. The spores are harmless. Several of the large mushrooms in the fungus forest are actually shriekers.
Chasm: The chasm roughly in the middle of the cave is 100 feet deep, and it grows narrower as one descends. Nothing of note lies at its bottom besides the bones of creatures unfortunate enough to fall within it.
Cliffs: The southern part of this side of the cavern rises in steplike cliffs. Each cliff is roughly 15 feet high. The ceiling ascends with the floor but with a more gradual slope. The cliff walls have a Climb DC of 20.
Other Cavern Inhabitants
A number of other creatures might inhabit the cavern, and the PCs could encounter them while exploring, resting, or during a fight with another creature. The following creatures are of a CR too low to be very threatening to PCs of a level appropriate to the challenge of facing the encounters in the area descriptions, but they might be interesting as noncombat encounters or as easier breaks between big fights. Also, one of these creatures could be quite challenging for a lone PC or one on the edge of a fight that has the other PCs occupied. You might also consider having multiples of these monsters confront the PCs, thus raising the difficulty of the encounter.
Area A: Dead Roper (EL --)
Read or paraphrase the following text when the PCs come within 60 feet of the roper's corpse.
Read or paraphrase the following text aloud when the PCs see the roper's corpse.
The roper from Room 21: Moving Day lived in this part of the cavern. The dead roper is a sibling that lived in the narrower caverns to the east. When new residents moved into those caverns, they chased out this roper and killed it. The roper from Room 21 heard the moving battle and fled, leaving its sibling to be killed.
The giant fire beetles have made little progress in eating the roper's tough hide besides worrying those wounds the roper suffered in the battle. If the PCs examine the corpse, a Heal check reveals some clues about how it died.
Area B: Purple Worm Lair (EL 12)
When the PCs approach this area, read or paraphrase the following.
When the PCs spot a purple worm egg, read or paraphrase the following.
The ovoid mentioned in the read-aloud text is one of many purple worm eggs in this chamber. A purple worm in the process of laying its eggs has picked this room as a nursery. Currently resting after a spate of egg laying, the purple worm lies beyond the stone walls of the cave. If the PCs approach within 40 feet of the pool, the purple worm detects them with its tremorsense and burrows up to burst from the pool in a shower of chilling water.
Purple Worm Eggs (8): Each egg is about 5 feet around and has a hardness of 8 and 50 hp. If the PCs don't destroy them, the eggs hatch in three days. Once hatched, the young purple worms immediately start burrowing in search of food. If you'd like to have the PCs fight the young purple worms, use the statistics for a giant constrictor snake.
Purple Worm (1): Use the statistics from the Monster Manual. The purple worm attacks until all the PCs are dead or all its eggs are destroyed. Note that the purple worm can burrow on this level of the cavern but other levels have hard bedrock that it cannot dig through.
Area C: Drow Ruins (EL 13)
When the PCs approach this area, read or paraphrase the following.
When the PCs move to within 5 feet of one of the doorways, read or paraphrase the following.
This ruin used to be part of a drow outpost in this cavern. The nature of the structure and the purpose of the individual rooms can't now be determined. The place was looted long ago.
The spirits of two drow remain here. Halaster killed these drow, a cleric and a wizard respectively, in a terrible battle that lasted hours. Infuriated by their tenacity, Halaster trapped their souls here as wraiths. Over hundreds of years, they have grown powerful -- if a bit crazed. Now dread wraiths, these undead lurk in the walls and wait for the PCs to reach the center of the ruin. Then the dread wraiths attack, one on each side.
Dread Wraith (2): Use the statistics from the Monster Manual. The dread wraiths attack until all the PCs are dead or until they leave the ruin. The dread wraiths cannot leave the ruin, but they can hide within the stone walls, floor, and ceiling so long as they don't move more than 10 feet into each area.
Adventure Hooks and Tie-Ins
Check out the Return to Undermountain: An Introduction for more details.
About the AuthorOnce Editor-in-Chief of Dragon magazine and now a game designer at Wizards of the Coast, Matthew Sernett wrote in a Dragon editorial that there's nothing in D&D he likes better than when the adventurers flee through the dungeon, running pell-mell through traps and past monsters because what chases them is worse. When he wrote that, Matthew was thinking about Undermountain.
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