389 Library of the Crescent Moon

Where to Add This Adventure

This dungeon is an ancient library lost to time. It is found in the depths of a desert, after a couple of days of traveling through the seas of sand and dunes. Use this module when the adventurers need to retrieve an old tome or book. The Crescent Moon Library could also work as the location of a special hidden object lost to time. The encounters and enemies presented in this module are intended for four to six 8th level characters.

Background Lore

The Moon Monks were the former occupants of this ancient place. The monks were a group of researchers of the unknown and the incomprehensible forces of the universe. These unorthodox investigators knew how to manipulate the fabrics of the world, and the energy of magic. If these people had used their strength to do evil, they might have been the despot overlords of many lands. But information and lore were their interests. And they worked day and night to find answers to the most complex questions.

The Crescent Moon Library is located deep inside a vast deserted land. To reach the library, one must approach the canyons. One of the cliffs features the only bridge to reach the ancient place. The Moon Monks were dutiful and dedicated. There were six of them, and they took care of each other as brothers.

Their will to learn exceeded most expectations. They were competitive even among themselves. Their obsession with learning and working resulted in the monks making a blood pact. They knew about an ancient ritual with which they could forgo their human needs like breathing, eating, and sleeping. They needed to build a clay statue that resembled each of them and stand beside it. The statues are impaled to the ground, symbolizing the death of their human needs. Then, they intonated the magic words while letting blood drip from their hands in the center of a circle. Even if this meant sacrificing their humanity, they thought the end justifies the means and went through with it.

The monks succeeded. They never felt tired again. Hunger and exhaustion were not part of their lives anymore. Their ability to research and available time doubled. Without the need to rest, every second was an opportunity. And so the monks became more and more versed in the mysteries of the world at the cost of their minds stopping working like those of a human. And their obsession with knowledge blinded their judgment and logical thinking.

The misguided monks started working with forces out of their reach. With a powerful ritual, they summoned a demon from the Abyss and imprisoned it in a cell they prepared for it. The powerful entity was not amused at all. The monks’ binding magic was effective; it could only scream in frustration at its failed attempts to escape. The monks did their homework and developed a remarkable cage for the demon. The monks wanted to understand the creature’s nature and study the demon’s immortality. Perhaps it was the key to abandon their humanity even further.

Since demons aren’t like humans at all, time doesn’t bother them. After a year in the cage, the demon noticed the monks were not ordinary humans anymore. The clever creature saw the monks were under the influence of a blood ritual. Laughing from the inside, it realized it only had to wait to be set free. It knew that kind of magic has a significant cost. Even powerful demons hesitate to pay it.

The demon was right. The pact allowed the monks to work restlessly, but their human bodies still suffered the consequences of going without sustenance and lack of rest. In a matter of weeks, the six monks were nothing but walking bones with loose hanging skin. They were already dead. The only thing keeping them going was the magic of the blood ritual. Their minds still craved knowledge.

One day, the demon saw the bodies of the six monks collapse one after another. Though the magic of the ritual still runs in what is left of them, their bones and bodies have no more force to move. Even with the monks gone, the demon still cannot open its cage. But it is just a matter of time. The demon is certain that one of two things is bound to happen. The cage suffers deterioration due to the passage of time and eventually allows it to escape, or a group of curious explorers or adventurers find the place and free it. Either way, the demon is patient enough. Time is all it’s got.

The Mission

The city of Atlas saw the Monks of the Crescent Moon be born. People in Atlas know about the six researchers that formed a group and found answers to the world’s greatest mysteries. However, the word in the city is that the monks used to come often to buy food and take a few days off. But one day they stopped coming and they were never seen again. This was decades ago, and today the monks are only a myth to the people of Atlas now.

Back then, the story of the monks drew the attention of a group of bounty hunters who thought they could find valuable treasure in the so-called ancient library. The not-so-brave mercenaries returned to the city like scared dogs. They claimed they found the place but it is inhabited by a horrible monster. The men described a giant beast with several limbs. One of them said it had pincers, another claimed it had talons and hooves. Though the descriptions of each of them don’t match, all of them agreed that they could hear the creature in their minds. The experience was so fearsome and strange to them that they could only flee in fear.

After this, it became a shunned location to visit for the people in Atlas. But Ficardus, a scholar, believes there must be a reason for the monks’ disappearance. He doesn’t have gold to offer, but he is certain the Crescent Moon Library is a place of wonders and forbidden lore. He tries to convince a group of adventurers of going. He assures it will be worth their while and that the city would reward such a service since the ancient library is a valuable asset.



Chaotic neutral human (age 48)

This old man wears spectacles that cover about 50% of his face. His long brown mustache and beard brim with white hair. He always has a spyglass and a magnifying glass with him. He has a friendly face and he has the habit of chewing tobacco leaves.

Personality Trait. “The world is full of unknown wonders; we must change that.”

Ideal. “I will become as famous as the Moon Monks one day.”

Bond. “I must find a way to see what happened with the monks in the ancient Crescent Moon Library.”

Flaw. “Me thirst for knowledge might drive me to do reckless things.”

Crescent Moon Library

The following descriptions of areas 1 through 9 correspond to the Crescent Moon Library and its surroundings.

Area Descriptions

Terrain. The library has deteriorated through the decades. Many sections of the floor tiles have cracked and sunk to the sand below.

Doors. The main double doors at the entrance of the library are broken. The mercenaries that visited the place many years ago forced the doors open and fled through here.

Light. Sconces with continual flame spells are present in areas 6, 8, and 9. The rest of the areas are in complete darkness if the place is visited during nighttime.

Smells and Sounds. The library is in complete silence. The smell of the foul river fills areas 4 and 9.

1. The Canyon

The monks built this bridge and placed a magic circle on it. This magic prevents the bridge from collapsing. The bridge is 5 feet wide and 15 feet long. It is not possible to see the bottom of the canyon; it is too deep.

2. Crescent Moon Circle

This is the magic circle that the monks used to make their rituals and spells. The monks carved a crescent moon on the stone’s surface and complemented the circle with a couple of magic runes. The circle is 10 feet in diameter.  A character can draw the last remnants of the Moon Monks’ magic from the circle. However, the blood ritual also affected the magical components of the magic circle and any spell cast with it goes bad for the caster.

A Passive DC 17 Intelligence (Arcana) check reveals the unnatural and unbalanced conditions of the magic circle. A character that uses the circle to cast any spell must make a suc­cessful DC 18 Constitution saving throw or drop to 0 Hit Points. Whoever uses the circle loses all their blood at once in a gory display.

North to the circle the doors of the main entrance lay broken on the floor. A faint smell of the dark matter river (area 4) reaches those who approach the library.

3. The Eternal Blood Pact

Six clay statues impaled to the ground surround a pool of crimson blood. This pool of blood never dries. The monks’ humanity is dissolved in this pond of red liquid. A gruesome reminder of their pact with the forces of evil. The six statues have faces of suffering and fear.

The magic of the blood ritual reanimates the six clay statues when the adventurers approach. The blood from the pool is absorbed by the six clay figures until they become red. The six figures combine into one being and increase in size and power. The red clay golem drips blood from its fists, and the faces of the six statues can be seen on the golem’s surface. If the adventurers flee this area the golem can follow them by squeezing through the 5-foot-corridors.

4. Dark Matter River

A part of the southwest wall of the library collapsed and allowed sand and dirt to take over a corner of this chamber. The monks used to have clean water here, but it has gone foul after years of corruption under the influence of the demon and the residual magic of the blood pact. A small 3-foot-deep pond continues to the east in a narrow 1-foot-wide stream.

The dark energy of the blood ritual tainted the water. It is now a thick pool of black goo. The viscous liquid travels slowly while bubbles seldom pop on its surface, releasing a foul stench. One black pudding attacks the heroes when they approach this area. The ooze creature chases the heroes as far as the entrance of the building.

5. Library Entrance

The library entrance leads to two sets of stairs to the east and west. The stairs descend 10 feet and give way to the main hall of the library and the demon cage (area 9).

6. Crescent Moon Library

Rows of ancient tomes, books, and scrolls are organized in several bookshelves. A stone dais in the center holds a large book. A successful DC 17 Intelligence (Investigation) check reveals many of the most recent topics that the monks were researching. They were exploring ways to travel to other Planes of Existence through magical gates in the layers of the Abyss. Other papers suggested the possibilities of casting the blood ritual in the whole city of Atlas, so no one would have to eat or sleep again. It is a miracle they did attempt this, otherwise, the whole city would be dead.

When the heroes touch any of the documents in here, a couple of the monk spirits return from beyond the void and chase the intruders in their library. Two ghosts traverse the walls of the library and attack the adventurers. The shadowy figures are nothing but vestiges of the humans they once were. Their enraged spirits fight until slain.

Secret Door. A passive Perception score of 16 or higher reveals the outline of a secret passage on the wall. Pushing a brick activates the mechanism and opens the way to area 7.

7. Secret Chamber

This small room has the statue of an angel on the west wall. In the center of the room, a large obsidian container rests on a one-foot-tall stone dais. Inside it, the leader of the monks stored the most secret treatises and the unique tome of blood magic. There is a defense mechanism installed in the lid. A passive Perception score of 16 or higher reveals there are small orifices on the north and south walls of the room.

Any creature that opens the black container must make a DC 16 Dexterity saving throw. Poison darts fly through the holes on the walls and target creatures in the room. On a failed save, the creature is poisoned for 1 hour.

Treasure. The ancient tome of blood magic contains several necromancy rituals and spells. Most of the book is written in an ancient lost tongue, but a character who wishes to learn from the tome and succeeds on a DC 20 Intelligence (Arcana) check, can copy the following spells to a spell book or write a scroll of them: plane shift, etherealness, instant summons, circle of death, create undead and legend lore. Additionally, the heroes find 3,213 gp, a roughly carved wood figurine of a queen, set with a hematite (60gp), a silver-framed painting of a tiger (180gp), and an ancient marble pendant, inlaid with mythril (250gp).

8. The Moon Stone

This room has sustained the passage of time. The floor and the walls look clean and remain in remarkably good condition. Three large plates are hanging on the north, east, and west walls. The monks used the different phases of the moon to enhance their magic. The plates reflect how the moon looks at all times. In the center of the room, on a 1-foot-stone dais, rests the moon stone.

The monks describe the stone in their texts. They talk of it as if it was made of moon rock. A closer look reveals it is made of ivory. The heroes have no other means to determine what was the real purpose of this place. But their presence here enrages the spirits of the former monks. Four wraiths come out of the plates on the walls and attack the heroes.

9. Demon Cage

The cage is a steel dome engraved with runes and binding spells. It is 15 feet in diameter. A small moat surrounds the center of the enclosing space but the dome covers it. The walls of the dome have large barred windows. People standing outside of it can see through and see whatever is trapped inside. A one-foot in diameter stone disk hangs from the dome’s spherical wall, pointing south. It bears a carved sigil of the moon.

The demon is aware that though the cage won’t kill it, it is best to wait for the cage to break or for someone to visit the ancient library. The demon is in a deep state of meditation when the adventurers arrive at the library. It has all the time in the world but that doesn’t mean it is not boring to be alone.

However, since the monks are gone, the residual magical energy from the blood ritual remains in place. This magic manifests itself in different forms. It corrupted the water, it twisted the monk’s spirits and turned them into restless undead. It also affects the binding magic that keeps the demon trapped.

The glabrezu in the cage wakes up when it feels the adventurers’ presence. At this moment, it realizes that a sufficient display of power might be enough to break the magic seals imprisoning it. This is because the chaos magic of the blood ritual has weakened the monks’ binding magic. The clever demon waits inside its cage for the right moment to escape. It plans to trick the adventurers by making them believe it won’t hurt them, and by promising the power of the demons. It plans to attack whoever approaches to free it with everything it has got and get rid of one enemy at the beginning of combat by grappling it.

First, it communicates with the heroes telepathically. It tells them the story of how it ended up here, and how the monks died. The demon tries to deceive the adventurers claiming that the cage is impossible to escape from. It tries to make a deal with them. The demon promises to grant them the power of demon blood and magic if they agree to set it free. A passive Insight score of 18 or higher reveals the demon is lying. If they accept, the characters only need to remove the stone disk with the moon sigil that holds the binding magic together. The demon makes the first move and attacks the first creature that approaches the cage and grapples it. If they refuse, it casts power word stun before breaking out its cage and attacking.


Ficardus is more than happy to see the heroes return. He introduces them to the city’s alderman and speaks on their behalf to convince him to send an exploring party to confirm the library is safe. The city of Atlas pays the heroes the hefty sum of 4,500 gp for their services.



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