The Emerald Vector: A Planar Adventure for Fifth Edition

Welcome, berk. You think you know the City of Doors? You haven't seen anything until the sky itself breaks. "The Emerald Vector" is a high-concept Tier 2 to Tier 3 campaign module that adapts the archetypal journey of The Wonderful Wizard of Oz into the surreal, philosophical landscape of Planescape.

It is a tale of displacement, artificiality, and the desperate search for home—all set against the impossible physics of the Great Wheel.

Part I: The Metaphysical Violation

Sigil is a closed system. The "sky" is usually just a haze of industrial smog and the flickering lights of the city curving overhead. There is no sun, and most critically, there are no stars. When the sky bleeds, reality is being rewritten.

The Inciting Incident

The party is engaged in a standard encounter in the Hive or the Ditch when the "Tornado"—a violation of natural law—strikes.

NARRATIVE: READ TO PLAYERS"The perpetual smog that chokes the air doesn't just clear—it burns away. In a heartbeat, the bruised-plum sky is replaced by a blinding, stark white void, like the color-drained vacuum of the Astral Plane. Four clusters of hard, static light ignite above you.

A low, 18 Hz hum begins to vibrate in your teeth, a pressure-sound that turns your stomach. The ground doesn't shake; it lurches, as if the city is trying to 'cough up' a foreign intrusion. The air suddenly tastes of copper and ozone."

The Four Constellations

The Hollow Man: A T-shaped cluster resembling a scarecrow or a crucified martyr. Its "head" flickers erratically, like a mind struggling to form a thought.

The Iron Heart: A dense cluster of blue pulsars beating with a rhythmic, mechanical frequency. It looks less like stars and more like a schematic for an engine.

The Beast: A sprawling nebula of red dust forming the outline of a crouching predator with a black-hole maw.

The Falling Girl: Not a static cluster, but a streak of golden fire—a comet on a terminal trajectory growing brighter by the second.

Part II: The Guardian at the Threshold

Standing between the party and safety is Gorm Gulthyn, the Dwarven deity of Vigilance. In this narrative, he is the "Wicked Witch of the East"—the immovable obstacle representing the tyranny of safety.

Encounter: The Avatar of Gorm

Challenge Rating: 20 (This is a survival encounter, not a fair fight).

Armor Class: 24 (Divine Plate + Shield).

Signature Move (Fire Eyes): As a bonus action, Gorm projects twin beams of intense red heat: $+15$ to hit, 22 ($4d10$) fire damage. If the target wears metal armor, they suffer the effects of Heat Metal with no save.

NARRATIVE: READ TO PLAYERS"The Sentinel stands before the portal, his divine plate glowing with a cold, golden light. He doesn't breathe; he simply watches with eyes that begin to ignite with searing crimson heat. 'None shall pass the Lady’s wards,' he intones, his voice like grinding stone. 'The Cage is sealed for your protection'."

The Deus Ex Machina: In Round 3 or 4, the "Falling Girl" constellation impacts Gorm at terminal velocity. The impact deals $100d6$ bludgeoning damage, obliterating the avatar into golden sparks.

Part III: The Travelers & The Patron

Emerging from the crater is Buff, a Giff Warlord who fell from the sky, and Steve, your enigmatic Patron.

The Cast

Steve (The Patron): Floats in a permanent, iridescent Otiluke’s Resilient Sphere. He wears a flannel shirt and jeans, marking him as a powerful outsider. He ignites a yellow ley line—the Yellow Brick Road—and tells the party: "Follow the vector. R04M knows the way".

Buff (The Dorothy/Lion): A boisterous Giff Warlord with a masterwork musket. He believes his "fall" was a tactical insertion gone wrong and is looking for his platoon.

R04M (The Scarecrow): A Rogue Modron or Warforged with a corrupted memory core. He knows the coordinates to the Green City but lacks the "why".

Part IV: The Path of Iron and Rust

The yellow ley line leads the party out of Sigil and into the Outlands, protecting them from the Psychic Winds.

The Rusted Autognome (The Tin Man)

The party finds a "Tin Man" in a state of body horror—a survivor of Ferrous Blight.

NARRATIVE: READ TO PLAYERS"In a clearing of grey dust stands a small, mechanical figure. Its joints are fused with thick, red oxide, and its face is locked in a silent, jagged scream. Three Rust Monsters circle it, clicking their antennae like gourmands waiting for the metal to 'ripen' before they consume its core."

The Mechanic: To recruit the Autognome, a player must use an action to perform "Surgical Lubrication" with oil or grease. Once freed, he joins the party as a Level 3 Barbarian with the Built for Success trait.

Part V: Oz-Themed Planar Encounters

The journey through the Outlands is fraught with surreal hazards.

EncounterThemeMechanicThe Vile OrchardThe Ents

Two Treants that throw Vile Fruit ($+10$ to hit, $4d10+6$ damage) causing Poison and Confusion.

The Poppy FieldsSleep

Crystalline Sensory Stones emitting red mist. DC 15 Wis save or fall into a euphoric sleep while taking $1d6$ psychic damage per minute.

The Cowardly LeonalThe Lion

Kurg, a CR 12 Celestial noble warrior who has lost his "Roar". He is currently terrified of a single Cranium Rat.

The Ether CycloneThe Tornado

A vortex of "possibilities" that reshapes terrain. Failure on a DC 14 Survival check teleports the party 1d10 miles off-course.

Part VI: The Joy-Stealer Demons

The "Flying Monkeys" of this realm are Joy-Stealer Demons—Tanar'ri addicted to the sensation of mortal fear and pain.

The Joy-Stealers

Description: Crossbreeds between mandrills and wasps wearing tattered Sensate silk vests and fez hats.

Flyby & Pack Tactics: They swoop in with advantage and do not provoke opportunity attacks.

Snatch Mechanic: On a hit, the target is Grappled and Restrained; the demon then attempts to fly them away.

Screech of Overstimulation: A 20-foot psychic blast dealing $4d6$ damage and causing the Stunned condition.

Part VII: The Green City & The Silent Monarch

The travelers arrive at Fortitude, the Gate Town to Arcadia. It is a walled garden of polished green stone and eternal emerald light.

The Lady's Intervention

The Wizard isn't behind the curtain. The Lady of Pain herself appears to address the anomaly.

NARRATIVE: READ TO PLAYERS"The Lady does not walk; she exists. She floats above the emerald grass, her bladed headdress casting long, sharp shadows. She raises a hand—not to cast a spell, but to impose a Rule. The Rule is: The Travelers Stop. Sound vanishes. Your vision tunnels into absolute black."

The Awakening: Steve intervenes by causing Astral Snow (crystallized thought) to fall. The entropy of the snow disrupts the Lady's temporal stasis, waking the party as the green gates swing open.