D&D Adventure: Crypt of the Forgotten King

This is a quick D&D one-shot adventure I put together using various tools, including Dungeonscrawl and GPT-3 from OpenAI. I’ve also got some Halloween one-shot ideas you can check out if you want. Enjoy!

D&D Plot Hook: Rumors about the king’s dead brother being buried in a crypt are circulating through the city. Players hear about the rumors. If they decide to investigate, they will be followed by a low-level half-elf thief named Errol who is trying to improve his skills as an adventurer. If they don’t notice him, he will make himself known later. He will be possessed and become the villain later. Players will have no difficulty finding the entrance to the Crypt of the Forgotten King.

AREA 1 – The Entrance

The entrance to the Crypt of the Forgotten King opens on the side of a cliff. The door is magically locked and must be broken open. There is a small hole hidden above the door which will allow it to be opened easily. Behind the door, players find a long, ten-foot wide hallway that burrows into the rock. As the players walk down this hallway, they will hear strange noises coming from behind them. This is Errol, the apprentice thief. He begs the players not to hurt him and let him tag along.

As players are talking with him, a horde of 2d20+20 giant rats will rush down the hall and attack. Errol will help the players fight and will be quite useful at this stage of the adventure. Once players finish killing the rats, they can move on with or without Errol. If they don’t want him around, he will slink away and promise not to return. He is lying and will come back to the players later. If players let him tag along, he will be excited and talk a lot, quickly becoming annoying.

AREA 2 – The Foyer

At the end of the ninety foot long tunnel, it opens into a foyer constructed of large, square pieces of stone. The ceiling is smooth, hexagonal rock with large holes (giant rat holes). Three squarish rooms make up the foyer. There is a door opposite the entrance. It is unlocked. Knocking sounds are heard on the other side.

When the door is opened, 2d4 skeletons will shuffle forward, wearing royal gear. If Errol is with the players, he will concentrate more on looting the skeletons than fighting them. The skeletons will spill into the foyer and attempt to attack all the players. They will fight until they are all killed. Players will find quite a bit of treasure on the skeletons, all of it royal jewelry.

If players take any of the items off the skeletons, a disembodied voice will moan, “No, no, no,” and 2d4 ghouls will climb out of the rat holes in the ceiling and attack. The ghouls will fight to the death and attack anyone in sight, including Errol if he is around. If he is around, he will flee and hide during this battle.

AREA 3 – Interior Hallway

Leading from the foyer deeper into the crypt, this hallway has two doors on the northern wall, two doors on the southern wall, and one door at the very end of the hallway. The hallway itself is in pristine condition and appears to have been constructed from carved stone blocks.

The doors have wooden handles and have no locks. If players get within five feet of any of the doors, the moaning voice will again speak, saying, “Don’t open it, don’t open it.” The players will have to make a saving throw versus magic.

Anyone who fails the check will have to roll on Table 1. Each player may have a different effect. They all happen at the same time, confusing the players.

TABLE 1

Roll a d20.

• 1-10. Nothing happens
• 11 – A blast of cold air shoots out of the door. The player closest takes 1d6 cold damage.
• 12 – A cloud of black smoke gushes out of the door. The player’s clothing and skin take on a bluish cast and he suffers a -2 penalty to his attack rolls for the next 2d12 hours.
• 13 – A blast of scalding hot air gushes out of the door. The player closest takes 1d6 heat damage.
• 14 – A blast of hot-purple fire comes out of the door. Roll 1d12. The player takes that much damage, ignoring armor and saving throws.
• 15 – A gust of freezing wind comes out of the door. The player closest takes 1d6 cold damage.
• 16 – A cloud of gaseous purple smoke comes out of the door. When it dissipates, it is replaced by a horrible, long-dead face. The ghost of whatever is behind the door appears and tries to possess one of the players, or perhaps all of them. Resisting requires a saving throw versus magic. Everyone who fails the check takes 3d6 damage. Only Errol is immune.
• 17 – A blast of blue fire comes out of the door. Players within ten feet take 2d8 damage. Those who pass a saving throw versus fire take half damage.
• 18 – A cloud of thick green smoke gushes out of the door. A disembodied voice tells the players, “Don’t do it or you will be sorry.” Anyone who passes a saving throw versus poison will have to make another saving throw versus poison. If they fail either check, they will be poisoned, losing one health per hour for the next 2d12 days unless cured. Health doesn’t restore naturally during this time.
• 19-20 – A thick cloud of green gas gushes out of the door. Anyone who fails a saving throw versus poison will take 1d4 damage.

While players are trying to figure out what’s going on – or arguing about it – the northwest door will open. A group of zombie goblins rush out. They are under influence of the Haste spell. Players must defeat the goblins. After the goblins are defeated, the disembodied and whiny voice will return, admonishing the players for making a mess. The voice will say something like, “No! Who is going to clean up all that green brain goo! Not me! You guys better get to work! If you don’t, I’ll be really mad.”

If players do not clean up the slime within one minute (impossible), the northeast door will open. A group of 3d4 skeletons wearing royal gear will rush out. If players don’t kill them immediately, they will attack the players. These skeletons are tougher than the earlier skeletons and require more damage to be taken down. Additionally, they all have the ability to cast Fog, Lightning Bolt, and Fiery Hand once each. As the battle begins to wear down, Errol will begin to mutate. If he isn’t with the party, he will stumble out of the northeast room.

The players watch in horror as Errol transforms into a thin, thin man with scraggly hair, thin arms, and thin legs. He will have thin black blood coming out of his mouth. His hands are thin claws. His eyes glow light blue. He may speak with a high-pitched voice or moan as he is possessed by the spirit of the King’s mad brother. He may growl or gurgle. He may hiss or whistle. He will say, “Who do you think you are messing with? Huh? Huh? Huh? Who? Huh? Don’t you know who I am?”

The thin man will rant for about one minute. When he finishes, he will say, “All right then, let’s get it on!” He will then attack the players, summoning 2d4 rat skeletons, 2d4 rat zombies, and 2d12 goblin zombies. He will use a variety of spells to attack the players, letting his undead minions do most of the damage. The thin man will say, “You guys are toast! Where are my rat skeletons? Where are my rat zombies? Where are my goblin zombies? Where are my wyrmlings?” He will cast Haste on all of his minions. He will cast Slow on the players. He will cast Magic Missile, Lightning Bolt, Fiery Hand, and Cloudkill if things get too dicey for him.

As the battle winds down, 2d6 wyrmlings will appear. These creatures should be an appropriate CR for the party. The undead worms are the size of snakes and fly/jump onto people before biting them. Anyone who is bitten by a wyrmling must make a saving throw versus poison or lose 1d4 health each round until cured. The wyrmlings can’t hit easily, but when they do, things can get bad quickly. As the players are dealing with this, possessed Errol, the king’s brother, will escape deeper into the crypt.

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AREA 4 – Northwest Room

Player see an assortment of barrels the rats have chewed through. They’re empty. A foul stench in the air is causing the players to gag. There is a patch of mold in the southeast corner. The patch is about 2-4 feet in diameter. The mold is magical in nature. If touched, the players must make a saving throw versus poison. Failure indicates that the players are affected by a Slow spell. The mold is somehow connected to the thin man, but there’s not many clues on how.

AREA 5 – Northeast Room

This empty room is scattered with bits of debris and rotting flesh. A putrid smell fills the room. A hidden cubby-hole in the northern wall holds 2d10+200 gp.

AREA 6 – Southwest Room

The door to this room opens quickly. On the other side, players find a bed. This is Errol’s sleeping quarters. There is a diary on a table next to the bed. The diary contains a detailed account of Errol’s life. His crimes to gain the king’s favor are outlined in great detail. The end of the diary details a change. Errol begins writing about a madness growing within him. The diary indicates that he has been possessed by a spirit – a spirit that used to be a king. In the bottom of the diary is a key that opens the chest in room number 8.

AREA 7 – Southeast Room

On the other side of the unlocked door is a meager collection of books, scrolls, and a few bottles of ink. This room contains a scroll that is written in Draconic. The players won’t be able to read the scroll. They will think the scroll is of great value, but it is a forgery and the meaning is nonsense. As players search the books, a darkness will descend from the ceiling. Errol trapped this room with a Darkmantle that will attack the players if they linger in the room for more than five rounds/minutes.

AREA 8 – Crypt Showdown

This is a hexagonal room with stone pillars in each corner. Glowing orbs of light floating on each of the six walls illuminates the area. A coffin, open, sits in the center of the room. If players approach the coffin, they will find a locked chest. The key from Errol’s room unlocks it.

Inside, players will find a note from the king’s godmother, explaining a way to stop Errol from being possessed. At this point, players can try to save Errol or try to destroy him completely. As they decide what to do, Errol will appear at the doorway to the room.

“You must not open the chest!” he screeches. “I’m warning you!”

This is the moment of truth. The players can try to destroy Errol or try to save him.

PATH 1:

If Errol is destroyed, the players will earn thanks from the king and the wrath of Errols Godmother, a woman named Natalie who will eventually try to get revenge on the players. Players who chose this path will get a Charm of Undead Control, more gold than they have currently, and 2d6 random potions.

PATH 2:

If Errol is saved, he will be grateful to the players. He will offer them a magic item of their choice. He will ask the players to go with him to the king and plead his case. The king will listen and Errol will be able to regain his title – and his land and wealth.

Errol will bring the players back to his home and give them each a magic item from TABLE 2.

TABLE 2

1. +1 Short Sword
2. Dagger of Envy – Players scoring a critical strike deal an extra +1 damage for each of their levels.
3. Potion of Cure Serious Wounds (5)
4. Potion of Cure Critical Wounds (3)
5. Wand of Charm Person (10 charges)
6. Staff of Illusion (25 charges)
7. Staff of the Woodlands (35 charges)
8. Staff of Fire (1 charge, 5d6 fire damage)
9. Ring of Protection +1
10. Ring of Protection +2

FINAL BOSS BATTLE NOTES

PATH 1:

If players are trying to destroy Errol, they will need to defeat him and more summoned undead, but it shouldn’t be too hard to do. The thin man will summon 2d10 wyrmlings. Possessed Errol will fight like a cleric, but he has limited casting options.

His ring of Control Undead is the secret behind his necromany powers, though he will warn players he is a powerful necromancer or even a lich. He is not that powerful, though. He will lie to try to intimidate the players.

PATH 2:

If players are trying to save Errol, they will need to defeat him by following his godmother’s instructions. This will involve several tasks, including 1) burying all the noble’s wealth, 2) removing Errol’s ring of Undead Control one way or another, and 3) Casting the spell written in teeny-tiny letters that are hard to read.

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Anyone attempting to cast the spell to stop Errol’s possession will need to succeed on a DC 18 wisdom save to successfullly cast the Godmother’s spell. Casting this spell on Errol will give him a second chance at life.

Monsters and Stats

Closing Notes

No matter which path players choose, they will have one group of nobles upset with them. While the king currently has more power, Natalie is cunning and looking to start her own damn kingdom.