Setting

The rural and peaceful village of Serenity’s Vale, located in a fertile valley surrounded by towering mountains. The village was known for its friendly inhabitants, serene views, and bountiful harvests. Today, however, it is a yawning chasm echoing the whispers of lost lives.

Level

Suitable for characters of level 5-8

Background

A massive sinkhole formed overnight, swallowing the entire village. The hole, which seems to extend into the very heart of the earth, is all that remains of Serenity’s Vale. Locals from nearby towns speak in hushed tones of a colossal creature burrowing under the earth, or of a mage’s experiment gone terribly awry.

Adventure Hooks

1. The party stumbles upon the hole while traveling.
2. They hear rumors in a nearby town and decide to investigate.
3. A desperate survivor from the village, who was away during the disaster, implores them for help.

The Investigation

The adventure begins with the party investigating the hole, which is over 100 feet in diameter. Within, an intricate network of tunnels and caverns stretches out, like a gigantic anthill. Perception checks and Survival checks may reveal traces of villagers and the nature of the calamity.

The Tunnels and Caverns

1. The Upper Tunnels: The remnants of houses can be found here. The party might encounter minor earth-related creatures or traps caused by unstable terrain. 
2. The Crystal Caverns: This area is filled with bioluminescent fungi and crystals that emit a soft glow. The party might encounter puzzles related to the light and reflections.
3. The Chasm of Echoes: This is a massive cavern where sounds echo back and forth. Stealth and perception are critical here, as it is the habitat of a fearsome cave creature.
4. The Lower Tunnels: Here the traces of villagers become more numerous. The party could find survivors, clues about what happened, or both.

The Climax

The hole was not the result of a creature nor a magic experiment, but the effect of a powerful artifact: The Orb of Deep Earth. A group of cultists from Serenity’s Vale had unearthed the artifact, intending to use its powers to create an underground utopia. However, they lost control of it, leading to the disaster. The cultists, now transformed into earth elementals due to prolonged exposure to the Orb, are the final challenge for the party.

The Resolution

After defeating the cultists, the party must decide what to do with the Orb. They might wish to use its power to restore Serenity’s Vale or seal it away to prevent further catastrophes. Some villagers might still be alive and need help getting back to the surface. 

Rewards

Depending on how they handle the situation, they may earn the gratitude of the surviving villagers, magical items from the village’s remnants, or even the Orb itself, if they decide to keep it.

Potential Future Plots

The existence of the Orb may attract powerful entities that wish to seize it. Alternatively, other Orbs might exist, causing similar problems elsewhere.

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The Orb of Deep Earth

The Orb of Deep Earth is a legendary artifact dating back to the earliest epochs of the world, when the primordial forces of earth and stone were raw and chaotic. Believed to be a relic from the time of the ancient Earth Elementals, this orb is imbued with their intense power and influence over the earthly realm. 

Wondrous item, artifact (requires attunement)

The Orb of Deep Earth is an item of immense power, its capabilities capable of altering landscapes at a massive scale. However, its power comes at a cost.

Appearance

The Orb is a perfectly round sphere, about the size of a human head. It appears to be made of a mix of various minerals and gemstones, swirling in a mesmerizing pattern of colors. It pulses with a soft, warm light that seems to come from deep within it.

Abilities

1. Terramorphing: The primary power of the Orb is the ability to shape and manipulate earth and stone on a massive scale. It can raise mountains, dig deep chasms, and create complex tunnel systems. The Orb responds to the will of its wielder, but requires a very strong mind to control, lest it unleash its powers uncontrollably.Once per day, the wielder can use an action to shape and manipulate earth and stone within a 1-mile radius, as per the Move Earth spell. The intensity and scale of the effect, however, are much greater and can create significant terrain alterations, such as raising mountains, forming chasms, or digging tunnel systems.
2. Elemental Transformation: Prolonged exposure to the Orb, especially when it’s being actively used, can lead to an individual transforming into an Earth Elemental. This transformation is irreversible and often accompanies a loss of the individual’s prior personality and memories.After every use of the Terramorphing ability, the wielder must succeed on a DC 18 Constitution saving throw or start transforming into an Earth Elemental. The transformation completes over 3d6 days. Once transformed, the character becomes an NPC under the Dungeon Master’s control, retaining only vague memories of its previous life.
3. Earth Mastery: The user can control earth-based creatures, manipulate earth-based spells, and has resistance or even immunity to earth-based attacks while holding the orb.While attuned to the orb, the wielder can cast Dominate Monster (earth-based creatures only) at will, without expending a spell slot. The wielder also has advantage on saving throws against earth-based spells and magical effects, and resistance to damage from earth-based attacks.

Drawbacks

1. Unstable Power: The Orb is not easy to control. A weak-willed user may trigger catastrophic events, as happened in Serenity’s Vale.If the wielder tries to use the Orb without being attuned, or if they fail a DC 18 Wisdom saving throw when attempting to use its Terramorphing power, the power activates randomly and could potentially cause a disaster, like a sudden sinkhole, earthquake, or stone rain.
2. Transformation: The Orb’s power comes with a risk. While the transformation into an Earth Elemental might be seen as a boon, the loss of one’s self and humanity is often considered a hefty price.
3. Drain: The Orb uses the life force of its wielder to fuel its powerful abilities. Prolonged use without proper rest and recovery can lead to serious health problems or even death.Each use of the Orb’s powers, other than Earth Mastery, drains the life force of the wielder. They take 4d10 necrotic damage that can’t be healed until they complete a long rest.

Destroying the Orb

The Orb of Deep Earth is incredibly resistant to damage. It can only be destroyed by submerging it in the molten core of a planet or by the combined will of four elemental lords.

Current Status

The Orb of Deep Earth was last seen causing the catastrophe at Serenity’s Vale, in the hands of a group of misguided cultists. Its current status is left to the outcome of the adventure.

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The Stoneheart Cult

The Stoneheart Cult was once a faction of the villagers from Serenity’s Vale who venerated the primal forces of earth and stone. They believed in living harmoniously with the earth, using its bounties judiciously, and respecting its might. When they discovered the Orb of Deep Earth, they saw it as a divine sign and believed they could use it to create an underground utopia. 

Transformation into Earth Elementals

The cultists, led by their charismatic leader, Thoren Stonehand, decided to use the Orb’s power to manifest their vision. However, prolonged exposure to the Orb caused them to slowly transform into Earth Elementals. The process was slow at first, but as they kept using the Orb, the transformation accelerated, until they lost their human forms completely.

Characteristics of the Transformed Cultists

As Earth Elementals, the cultists retained a portion of their human consciousness, enough to continue their purpose, but lost their human empathy and broader perspective. They are formidable foes, possessing the physical prowess of Earth Elementals, enhanced by the raw power of the Orb. 

Encountering the Cultists

The final encounter with the Stoneheart Cult is designed to be a challenging fight for the party. Here are some ideas for running this encounter:

1. Terrain: The battle takes place in a large cavern, with the Cultists using the Orb to dynamically alter the terrain to their advantage.
2. Numbers: The Cultists should outnumber the party, but they should be divided into smaller groups that the party can tackle one at a time, leading up to the final confrontation with Thoren.
3. Thoren Stonehand: Thoren, the Cult leader, is the strongest of the Earth Elementals. He possesses a unique ability to use the Orb’s Terramorphing power in combat, creating sudden pillars of rock, fissures, or even stone barriers to hinder the party.

Stat Blocks

Consider using the Earth Elemental stat block in the Monster Manual for the regular Cultist Elementals, but add some variety in their abilities, like hurling stones, creating minor tremors, or summoning stone walls. For Thoren, use the same stat block but with additional hit points and the aforementioned unique abilities. Adjust the difficulty as needed to provide an appropriate challenge to your party.

Aftermath

After defeating the Stoneheart Cult, the party will have to decide the fate of the Orb, potentially setting up future adventures.