The Frostheart

Intro

Snow bites at your cheeks as a bitter wind cuts across the high mountain pass. Jagged peaks loom around you, their shadows stretching long in the pale winter light. Snow crunches underfoot as you push forward, the world muffled by the thick white drifts. Around you: nothing but ice, rock, and sky—endless and desolate. You're searching for the entrance to a long-forgotten cave said to be the source of the interplanar bleeding causing the glacial anomalies in the region.

Finding the Cave

Terrain Effects: Due to the raging wind, ranged weapon attacks suffer a -2 penalty to hit

Players have tracked the source of the elemental bleeding into the material plane to this region, but it must be within a cave somewhere on the mountain side. Players may find the cave with the following:

• DC 14 Survival (Disadvantage due to the snow, unless the character has a background living in harsh winter environments) - Following the contours on the mountain side is tough with the blowing snow, but you manage to follow one to a small rock out cropping, within the rock outcropping, a cave entrance is seen
• DC 15 Arcana - Honing in on the arcane energy bleeding through the rift, you are guided, almost as if there is an invisible trail of arcane energy leading you. Following the this, you come upon a small rock outcropping with a dark cave opening in the middle
• DC 14 Investigation - (Disadvantage due to the snow, unless the character has a background living in harsh winter environments) - Moving from one vantage point to another, you manage to spot a darkness within a small outcropping which appears to be the entrance to a cave

Should the players fail to succeed on either of these DCs, they will eventually happen upon it, however due to the prolonged exposure to the elements, they each receive 1d8 cold damage and have disadvantage on their initiative roll against the Ice Troll - Unless they have resistance to cold damage.

Ice Troll

As the players begin to approach the rock outcropping, An Ice Troll emerges violently from the trees and attacks the players. (You may wish to add 2 Winter Wolves to the encounter, if you want to pose a greater challenge to the players).

The Cave

R1 - Cave Entrance: The mouth of the cave yawns open like a jagged wound in the mountainside. A shimmer of frost crystals rims the stone, glowing faintly blue. The air inside is unnaturally still, and despite the howling wind falling dead the moment you step within, an occasional cold air pulses inward.

DC 13 Arcana - The glow created in the frost is a result of planar residue, common in rift-affected sites.

R2 - Statues: A rectangular hall, twenty feet wide and stretching nearly fifty feet, opens before you. Along both side walls, rows of humanoid statues stand perfectly still, spaced evenly apart on either side of a central aisle. The figures vary in race, gender, and dress—but each is captured in a moment of panic or pain. The air here is unnaturally still, and your breath fogs visibly in front of you, hanging motionless. A layer of frost covers everything in a thin film.

DC 14 Investigation - The statues are real people, flash-frozen in time.

R3 - Ice Crossing: A narrow, arched bridge of translucent blue ice spans a yawning black crevasse. The gorge drops away into shadow, and the bridge—barely five feet wide—is slick and uneven underfoot. The wind here is a living thing, shrieking across the chasm in bursts that rattle your gear and sting your eyes. Pale mist rises from below, swirling in ghostly patterns around the edges.

Skill Challenge: Players must traverse the 60ft bridge, fighting against strong gusting wind surges and a slippery surface.

Mechanics: Every time a character travels 20ft on the bridge, they must succeed on a DC 14 dexterity saving throw. Failure:

• DC 15 Strength Saving Throw - Grab onto the bridge, preventing from falling
• DC 15 Dexterity Saving Throw - Regain footing before falling

Failure will result in a player falling 40ft, receiving 4d6 bludgeoning damage. A player who falls cannot be seen below, as the reflections around create an optical illusion of an endless pit. They can, however, be heard.

R4 - Glacial Vault: You step into a large, circular chamber enclosed beneath a crystalized dome of translucent ice. The ceiling arches twenty feet overhead, refracting faint blue light that dances across the smooth walls. All around the perimeter, weapons and relics are embedded in the ice like insects caught in amber—shields, blades, scroll cases, even a broken staff. At the center of the room, a raised dais of solid frost juts from the floor, its edges chiseled and sharp. Resting atop it is a stone chest, rimmed with frost and half-buried in a crust of ice.

The Chest: The chest gives off a strong magical aura to those attuned to magic. A successful DC 14 Arcana check will reveal the aura is Abjuration magic. DC 16 will also reveal a faint Evocation aura radiating from the chest.

No visible lock or mechanism can be seen on the chest, in order to open the chest, a player must cast a spell of first level or higher on the chest.

Trap: If the spell cast on the chest was an Abjuration spell, the trap is not triggered. If the spell cast to open the chest belonged to any other school of magic, the evocation glyph attached to the chest will activate, sending out a blast of frost which envelopes the room. Each creature in the domed room must succeed on a DC 14 dexterity saving throw, taking 4d8 cold damage on a fail, or half as much on a success.

The ice around the room has a strange, extra-planar aura and cannot be broken to retrieve the items frozen within.

Loot:

• Ring of Cold Resistance
• Bead of Enduring
• Wand of Curing (5 charges - Cure Wounds and Healing Word can be cast from first to fifth level, each cast reducing the charges by the level the spell was cast at. ie...You can use 5 charges to cast Cure wounds or healing word once at fifth level, or use 1 charge at a time to cast either of them up to 5 times.

R5 - Shards of Reflection: A square chamber about thirty feet across opens before you. Four tall, freestanding mirrors of polished ice stand in each corner, their surfaces fogged with a thin layer of frost. The light in the room seems to bounce and bend in strange ways—reflections flicker across the glass with impossible movement. At the exact center, a pedestal made of translucent ice rises waist-high from the frozen floor, cradling a swirling orb of pale blue frost.

The mirrors

• Mirrors are blank upon entry
• If a player approaches one of the mirrors around the outside of the room, a brief, animated scene will play out on the mirror
• The mirror in the center remains a simple mirror until all four mirrors scenes have been activated
• Each mirror has a frozen hand print at the base
• In order to activate the center mirror, each of the other 4 mirrors need to be activated from a player placing their hand on the mirror
• When a player places their hand on the mirror, they receive 1d6 cold damage and a rune on one corner of the mirror in the center ignites
• Activating the four mirrors, activates the center mirror

When the center mirror has been activated, read: As the fourth mirror is activated, the final rune on the mirror in the center ignites. The once reflective surface shimmers and fades, almost as if looking into water.

Players may move onto the next room by entering the mirror

Mirror images - The mirrors are listed below in order of activation, as well as a description of the scene they represent;

1. The frost-rimmed mirror fogs over, then clears with a soft hiss of escaping cold. You see a high mountain plateau beneath a slate-gray sky, windswept and silent. A slender elven woman in a fur-lined cloak stands barefoot in the snow. Her white hair whips in the wind, and her violet eyes glow faintly with arcane energy. She holds a scroll case out in both hands, arms trembling slightly as she faces a towering frost giant clad in tribal armor of leather and bone. The giant studies her in silence, then slowly kneels. Between them, a brazier burns with pale blue frostfire. As the giant reaches forward, she mirrors the motion, and together they press their hands into the flames. The fire flares outward in a spiral of light. Snow begins to fall gently, muffling all sound. The image fades as the two figures stand, not as enemies, but as equals.
2. The mirror flickers to life with a crackling pulse. You see a vaulted hall of ice, grand and solemn, its walls veined with glowing blue lines of arcane script. A wide staircase rises at the far end to a crystalline throne flanked by curling spires of frost. The mage—now dressed in a regal robe of silver and sapphire—ascends the stairs slowly. Her footsteps echo in the hush. Below her, rows of humanoid figures—elves, humans, dwarves—kneel in silence, their heads bowed in reverence. A ceremonial staff of twisted ice rests in the mage’s hands. As she turns and sits upon the throne, her eyes glow with cool blue light. She does not smile. The hall remains silent as the vision fades.
3. The scene shimmers into view slowly, as though forcing its way through thick frost. A circular ritual chamber is carved deep into ice, its ceiling high and rimmed with jagged icicles. The mage stands alone in the center of a glowing glyph circle, arms raised, her hair floating weightlessly around her. Surrounding her, two dozen followers stand in a solemn ring—robed, armored, unarmed—watching her with expressions of trust and awe. But as the glyphs pulse brighter, frost erupts from the mage’s feet, racing outward in jagged lines. The followers gasp and try to step back, but their feet are already frozen in place. Ice coils up their bodies like vines, freezing them mid-motion. Their faces twist in betrayal and fear. Behind the mage, the frost giant steps into view from the shadows, lifting a massive greataxe above his head. As the last follower freezes solid, shimmering trails of icy energy snake from each statue and converge on the giant’s blade. He roars in triumph as the axe glows with power. The mage does not flinch or turn—her expression is cold, distant. The mirror dims.
4. The image appears in jagged flashes, like a half-remembered dream. You see a narrow ice tunnel, slick and uneven, lit only by the pale blue light of arcane torches. The figures in the scene are unmistakable: your party, stumbling forward with weapons drawn and breaths fogging thick in the air. Frost creeps along the floor behind them like a living thing, spreading quickly. One of you turns to shout a warning—then is seized by a burst of rime and frost, body rigid as ice climbs over their face. Another slips, calling for help, but their voice is cut off by the crack of freezing limbs. One by one, you fall, encased in glittering ice. The tunnel goes quiet. The image lingers, the final tableau of your frozen bodies etched into the glass, before the mirror goes dark.

R6 - The Echoing Hollow: A circular room carved into the glacier opens quietly around you, its floor uneven with drifts of snow and patches of cracked ice. At the far end, a kneeling figure in white robes hunches beside a frozen corpse sealed halfway into the wall. Her back is to you, and her sobs are faint but audible—each one echoing unnaturally long across the icy walls. A single, guttering magical lantern glows dimly beside her, casting long shadows along the cracked floor.

RP Encounter: Lyrielle came to this frozen ruin searching for her brother, Caelun, a gifted scholar who left months ago to join what he believed was a noble cause: an expedition led by a mysterious mage who promised protection, knowledge, and power to a chosen few. He sent one final letter—cryptic and urgent—before vanishing.

She tracked her brother here, she has been here 3 days but cant bring herself to leave her brothers side.

What she Knows:

• Caelun and others followed a powerful elven mage, a woman never named in full, but whispered about as “The Winterheart” or “the Ice Mother.”
• She believes the mage made a pact with something not of this world—a being of winter from another dimension. From what she’s pieced together, this being offered power in exchange for establishing a foothold in the material plane.
• The frost giant seen in visions and carvings may not be a mortal creature at all, but a manifestation or avatar of the pact itself—a bridge between realms.
• She has no desire to go further, but warns the players: “The cold doesn’t kill quickly. It makes you forget. She’ll offer you safety, even purpose. You have to say no before you believe her.”

Optional Insight (DC 14) - She appears to be hanging onto some lost hope. You now notice that she clutches her holy symbol around her neck, with a faint blue glow emitting from between her fingers.

• If pressed: She confesses that her holy symbol glows faintly when she nears the mage’s trail—an old relic of sunrise and light that reacts to deep magical cold. If convinced, she gives it to the party as a warning charm (grants resistance to cold damage once, then crumbles).

If the players convince Lyrielle to join them, use the stat block in the Resources section below.

Letter From Brother

R7 - Vault of Silence: You pass into a chamber shaped like a perfect octagon, with walls of deep blue ice and a high, domed ceiling. The moment you enter, sound vanishes—your footsteps make no echo, and even your armor seems muted. A faint pulse of light moves along rune-etched lines carved into the walls. In the center of the room lies a raised tile, just slightly misaligned with the rest of the smooth floor.

Arcana DC 15 - The center of the room is a null-magic field (magic is suppressed)

Perception DC 14 - A faint line on the raised tile stands out slightly. Following the line, it leads to a shallow recess in the side of the tile.

• If a player inspects the recess, they will discover it activates the tile, which will rise up, revealing a compartment underneath with a crystal.

Null-Magic Crystal - This faintly glowing crystal hums with suppressed arcane energy. A creature carrying this item gains the following benefits:

• You have advantage on saving throws against spells and other magical effects.
• When you take damage from a spell or magical effect, you instead take half damage
• After you are affected by a magical effect, whether or not you succeed on the saving throw or take damage, the crystal’s protective properties are disrupted. You lose the above benefits until the start of your next turn.

R8 - Elemental Node: This wide, oval room glows with pale blue light that seems to come from the air itself. Suspended ten feet above the center is a massive, crystal-like shard of elemental ice, slowly rotating in place. Beneath it, a circle of arcane runes is carved into the floor, glowing faintly and releasing occasional spurts of frozen mist. The temperature here is frigid even by the cavern’s standards—your joints ache, and your breath feels sharp.

Crystal:

• If a player touches the crystal, they must succeed on a DC 14 wisdom saving throw. On a fail, they take 3d6 cold damage and, the next time the player takes cold damage, they have vulnerability to cold. On a pass, they receive half damage and do not gain vulnerability.
• Arcana DC 16 - The crystal appears to be amplifying the planar bleed. Destroying it could possibly subside some of its effects.
• The crystal is destroyed if it receives any amount of spell damage
• If the crystal is destroyed, Virellia loses 1 legendary resistance, and 1 legendary action per round.

R9 - Lab of the Fractured Mind: A rectangular chamber stretches thirty feet long, cluttered with overturned furniture and shattered glass. Fractures run like veins across the floor and walls, with jagged ice spiking upward in places. Several tall bookshelves lie toppled or broken, their pages fused together with frost. A worktable stands against the far wall, partially encased in ice, with ink frozen mid-stroke on the parchment scattered atop it.

Searching through the documents, the find the following entries:

R10 - Mirrored Hallway: The hallway stretches before you like a frozen artery. Smooth ice makes up the walls, ceiling, and floor, gleaming in the pale ambient light. On the left wall, four evenly spaced torches sit in iron sconces—each unlit. At the far end of the hallway, a frozen wall with shards of ice protruding in various directions, at the walls center is a large, snowflake engraved into the wall, with a small recess in the middle.

As you step in, your reflections appear in the mirror-like ice wall opposite the torches. But something is wrong—they don’t match your movements. One by one, your reflections drift to stand beside different torches in the mirrored version of the hallway.

Setup Instructions

As the party enters the icy hallway, they see four unlit torches mounted on the left wall (Player side), spaced evenly apart. On the opposite wall (Reflection side), the torches are mirrored. These torches are not labeled or coloured in-world, but for reference, player side is coloured, reflection side is numbered:

• Red - 1
• Orange - 2
• Yellow - 3
• Green - 4

A player may interact with any of the torches, but a torch will only light if it is the torch opposite their reflection. When a player lights a torch, the reflections will respond to the lit torch by lighting and/or extinguishing a mirrored torch. To solve this puzzle, all the torches in the reflection must be lit. Once the reflections react to a players torch being lit, the players torch extinguishes, but the corresponding reflections do not.

Setup

To setup for the puzzle, reference the charts below (note: a lightning bolt over a line indicates that the colour corresponding to the lightning bolt extinguishes that torch when lit)

Assign each players reflection to 1, 2, 3 or 4. You may also wish to set up a visual representation for the players. If you are playing with miniatures, place each players mini on one side of a hallway. Opposite them, place something opposite their mini to represent their reflection. Then, when a torch is lit, place another object either on top of, in front of or beside the reflection to indicate it is lit. update the placement as the players light their torches.

I am sure there are several ways this works, but the two main ways I can think to light all the mirrored torches are the following sequence:

1. Any order of three torches lit first: Red, Orange, Yellow
2. Green lit fourth
3. Yellow relit last to restore Torch 4, which was extinguished by Green

OR

1. Orange/Green
2. Green/Orange
3. Then Red/Yellow in any order

This results in Mirror Torches 1, 2, 3, and 4 all being lit simultaneously.

Once all four mirrored torches are lit, the reflections will clap, but no sound is heard. One of them will then appear to walk closer to the wall, and extend a hand, grasping a Key, coated in ice. A player may reach out and grab the key from the reflection.

Inserting the Frost Key into the snowflake melts the wall, revealing the throne room

R11 - Throne of Hollow Frost: You descend a wide staircase carved from sculpted ice, its steps perfectly smooth and slightly concave. The room opens into a vast, circular basin—fifty feet across and ringed by pillars of frozen mist. Crystalline arches stretch from the ceiling to the floor like frozen ribs. Opposite you, a jagged throne of sculpted ice rises from a mound of blue frost. Calmly seated upon it is a woman with snow-white hair and pale blue skin, her silver robes fluttering in a wind you can’t feel. Beside her looms a massive frost giant, unmoving, his eyes locked on yours. The woman, rises slowly:

“It’s a rare thing… to arrive willingly. Most stumble into this place by accident. But you... you climbed.”
“Tell me—was it curiosity that brought you here? Or fear?”

Note: For some reason Virellia's stat block did not include Legendary Resistance. She has 3 (unless the crystal was destroyed, then she has 2).

Optional Roleplay - If players engage with her in conversation, she responds without anger. She speaks like someone who truly believes she's offering salvation. She will offer the players to join her, and be part of something greater.

Sample dialogue:

• “I offered them peace when your world gave them none.”
• “I only took what was given freely. Will you offer the same?”
• “You saw what I gave them. Stillness. Purpose. Unity. No more pain. No more fire. No more endings.”
• “The world beyond the ice has no storm. No blood. It is vast, and clean. I only opened a door.”

Combat is initiated if the players act with open hostility or she feels they cannot be persuaded to join her.

Final words before initiative - “I offered you stillness. You chose violence.”