No Prep Module: Underdark Assault for D&D or RPGs

This adventure can be can be easily customized to a party of any size or level or run as a level 8 adventure for 5 players. It can work as a small side adventure in an existing campaign, as a standalone one-shot, or the start of a new adventure. Use the links to the tools in their relevant section to customize the adventure to your party.

Underdark Assault

Barrheller is a defensible-looking city with imposing walls and an alert garrison, and has been the site of many battles. Positioned within a desirable mining spot near the edge of 3 borders, it has frequently changed rulers throughout history. The halfling kingdom of Zelterry conquered the city 5 years ago during the previous war and now stand as the rulers. The rich mines have usually made this a prosperous city, but signs posted warn citizens to stay away from the mines, and the city looks like it has fallen on hard times.

The Priest: Watson Strongbones, Male Halfling. Description: He prefers to wear the grand gowns of high society. He carries his fan with him everywhere and carries himself as the perfect gentleman. He has a slight overbite and is overall scrawny. He is baby faced with chestnut hair.

  • Use this for the town: Barrheller. As the players explore the city and maybe inquire about the mines, they'll come across a priest looking for help.
  • A priest has lost his voice and can't perform service. He'll ask hoarsely if any of the PCs can run his service, focusing on divine characters. He worships the same god as any of the divine characters and will focus on them, but is grateful for help from anyone.
  • If any of the PCs agrees to help, have them perform the service and make appropriate skill checks to what they're saying. Persuasion if it's hopeful, Intimidation if it's not, or anything that matches.
  • Do 2-3 checks, with the outcome determining how well the service goes and how receptive the congregation is. The priest will thank them and give them a potion of holy water. Also, secretly, the priest will go with the PCs while staying out of sight and heal them randomly through the adventure without revealing himself.

After dealing with the priest and exploring the town more, they can find a much more substantial quest. At this point in their careers the players are likely becoming minor celebrities, and can be asked for by name from the baron. Or they might go looking for quests and learn the baron is trying to improve the town's defenses from impending drow attack.

"We've been getting raided constantly by duergar and drow ever since the mines breached the underdark." He looks grim, "had to close them down, put a lot of folk out of work, and the raids keep coming. We've already lost so many, but I fear they won't stop until everyone is gone.

The Baron: Stannor Nimblefingers, Male Halfling. Description: A man with thick toned arms and a paunchy gut. He wears a tan shirt, with a brown mid length shorts with brown tights and flats, usually wearing a coat over them. His auburn hair is smooth and relatively long. His eyes are brown and catlike.

  • The baron has been dealing with increasing raids from the underdark, targeting both the town and their mines. People have been kidnapped or killed, and their supplies devastated.
  • He will offer the PCs 1,000 gold to drive off the creatures and reclaim the mines, as well as any items they find so long as they leave the ore.

Once the party gets any supplies they need and complete any other business they have in town, you can continue.

The path continues down along a sheer cliff face, that twists around the edge of the wide canyon at the center of the valley. Looking along the path you can see a mix of natural and artificial bridges that line the gaps in the rocks, once used to ferry ore out of the mines. As you approach the edge of the cliff you can feel the wind wooshing past your face, sucking air down into the deep canyon with strong downdrafts.

  • The party is attacked on the cliffs. If you're using a battle map, try to make good use of steep cliffs and narrow paths. Ending your movement on bridges or close to the edge causes them to be blown by the downdrafts, requiring a DC 10 Acrobatics check to avoid falling prone.
  • After continuing along the bridges, they'll find two abandoned barrels of tar weighing 200 lbs each.
  • The entrance to the mine is a bit further down.

Dungeon Map

  • A green flame inside a glass sphere is trapped in the webs within room 8. It must be carried to room 4 and used to light the brazier. There are multiple spheres hanging in the webs, which might be necessary because the mines are frequently hit by earthquakes.
  • When the party travels to room 5 or 6, have an earthquake hit and require the person carrying the sphere to make a DC 15 Acrobatics or Sleight of Hand check to keep hold of it. If they have some other solution to keep the sphere safe, that can work too. Failure causes the glass to fall and shatter, snuffing the green flame.
  • If the players move slowly or retrace their steps, you can have earthquakes happen occasionally either every few rooms or 10-20 minutes.
  • The locked door in room 4 has a brazier that requires green flame to open the rock wall.
  • When the party reaches room 3 they find corpses from a battle, some of which are splattered against the walls from the hidden spring trap.
  • At the second to last room, they come upon the following:

You come to a room in the mines that appears to have once been a small camp, but has long since been abandoned. Most of the remaining supplies have decayed heavily, with a couple torn and rotted tents, and some old hides encircling a pit of charcoal. The only object remaining in good condition is a large rectangular mirror along the far wall. In the mirror's reflection you can see the same room, but in much better condition. The camp is complete and in good condition, with lights illuminating the area. Next to the firepit in the reflection is a man in robes, his back is turned to you and he hasn't taken notice.

  • The man can't hear them from outside the mirror, but the mirror itself can be stepped through to enter the scene inside.
  • By stepping into the mirror they can explore the mirror realm, but when they turn to leave, the portal refuses to open. They're trapped in the mirror room.
  • The man in the mirror is the priest from earlier, he'll admit to following them to provide healing from afar but got stuck in the mirror.
  • The trick here is to exit facing the same direction as they entered, by walking backwards through the portal.
  • As they reach the final room, read this:

Underdark Cavern

An exploratory tunnel leads into a massive cavern in the underdark. From your vantage point, you can see a cavern almost a mile in size, with patches of fluorescent moss on the walls that illuminates the distant edges. The floor of the cavern is lit with hundreds of torches and braziers, carried by a drow army that looks to be made up of at least a thousand soldiers strong and war machines. Many of the soldiers are enslaved creatures, with an elite drow command of maybe a hundred.

  • Attacking the army here directly is almost certain suicide, but when the players decide to leave to warn the town or whatever else they're caught by a scouting party and will need to fight to prevent them from reporting back to the army.
  • The army is marching upon the town, so the PC's will need to hurry back to Barrheller to help defend it, otherwise it will be wiped out.
  • For the finale, you can run it as part skill challenge and part combat. The baron has received word from the king that reinforcements are coming to help, but probably won't arrive in time for the initial assault.

It's late at night when a scout on the walls shouts a warning that the drow army is approaching. As you look out onto the field below, you see the same army from the underdark marching on the surface. As they march, you see them start to erect siege towers with large steel umbrellas that fan out and shield the army from the sky above. You can also see sinister looking trebuchets being assembled as the army comes to a stop about 900 feet (270 meters) away.

  • If the PCs decide to help defend the city, then the goal is to hold out against the army long enough for the king's levy to arrive, which could take a couple days.
  • The drow army will lay siege to the city in the meantime, and it's up to the players to help defend. Ask what they want to do, and have them make relevant skill checks. Low checks result in random encounters, with an encounter difficulty based on how low the roll was.
  • The umbrellas are there to protect from arrows and also the harshness of the sun, should the PCs decide to perform any daytime assaults.
  • If the players brought the barrels of tar with them and decide to use them, give advantage on any resulting check.
  • Use the Encounter Generator to quickly generate encounters as needed. Set the environment to Underground, and you may want to throw in a couple drow with whatever else.
  • After defending against the siege and assaults, the king's army arrives and launches the counter-offensive. You can run this as a combat if you like, but it may work better if you just have the players make a couple attack rolls and describe how effective they are in the final battle. The king's army will win handily either way.
  • If they hold out and drive back the drow army, the king agrees to station additional soldiers to help protect the against future underdark incursions and allows the mines to reopen.

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