The Gray Sits at the Bottom of Zaun and Thins as You Climb
Our Atlas puts the smog over Zaun’s lower levels and canyons, and our entry on the Sump says the air only clears toward the upper city.
Ekko, an inventor, grew up in Zaun, the undercity beneath Piltover. Piltover is the richer city built above it. Ekko watched what the bottom of Zaun did to his family. His biography says he “watched his parents age beyond their years, toiling for too many hours under dangerous conditions in suffocating factories.” His parents, Inna and Wyeth, wanted him out, because they believed “Zaun, with all its pollution and crime, would only stifle Ekko, whom they felt deserved the wealth and opportunities of Piltover.”
The worst of that pollution has a name. The Zaun Gray is the smog that fills the bottom of Zaun. It is known as the Gray for short, and our Atlas, RuneGrove’s encyclopedia of places, is exact about where it sits.
The Zaun Gray is the permanent toxic smog that hangs over the lower levels and deep canyons of Zaun, the undercity beneath Piltover. It is the byproduct of decades of unregulated industry and reckless chemtech experimentation, and it blankets entire districts so completely that little natural light reaches the streets.
From our Atlas entry for the Zaun Gray.
The Sump is Zaun’s lowest level, and our entry for it says the air there improves in one direction only.
It is home to the most desperate and destitute of Zaun’s citizens, and even the air here has a texture to it, a thickness that only clears as one climbs toward the upper city.
From our Atlas entry for The Sump.
In Zaun, the higher you are, the cleaner the air you breathe. The ways Riot has written for moving through the city run upward, out of the Gray, and they are not open to everyone.
In Zaun, the higher you are, the cleaner the air you breathe.
The Factories Feeding the Gray Never Stop
Our Atlas says Clan Ferros’s synthetic hex-crystal plants in Zaun are rumored to feed the Gray, and that the clan protects them so they never stop.
The Gray does not blow over, because the industry making it does not stop. The industry our Atlas singles out belongs to Clan Ferros, a Piltover merchant family that makes synthetic hex-crystals for hextech, Piltover’s fusion of magic and engineering.
The synthetic hex-crystal manufacturing run by Clan Ferros in Zaun has long been rumored to contribute heavily to the Gray, and that production is protected through espionage, intimidation, and murder so the factories never stop.
From our Atlas entry for the Zaun Gray.
The rumor goes back to the biography of 
Camille, one of the clan’s own, which says “synthetic crystal manufacturing has long been rumored to heavily contribute to the Zaun Gray.”
From Camille’s biography.
A note on Camille’s biography. Her biography also says where the clan’s crystals came from in the first place: the brackern, giant crystal-bearing scorpions. That account was written before Riot updated 
Skarner, the brackern champion, and the Skarner update changed the lore of the brackern. His biography now calls him “the ancient protector of Ixtal” and says he “shaped the earth itself and built the first arcologies,” the great cities of Ixtal.
Camille’s biography still tells the older version of the brackern, so it is likely to be updated to match the new lore. This piece leans only on what her biography and our Atlas say about the Gray, not on how the clan first got its crystals.
The Atlas does not put all of it on one clan. It also says the Gray is fed by Zaun’s own inventors, the ones who find Piltover’s ethical restrictions too confining and make volatile chemtech, Zaun’s cruder chemical technology, without oversight. A Piltover clan’s factories and Zaun’s own labs feed the same cloud, and neither is going to stop, so the air does not clear. People who want cleaner air have to go up to it.
Down in the Gray, You Cannot See Where You Are Going
Riot’s short story Deep Breath describes a Grayout you cannot see through, our Atlas says the lower city runs on artificial light, and predators hunt couriers through the smoke.
At the bottom, the Gray is a problem for your eyes as much as your lungs. Deep Breath, a Riot short story narrated by a young man in Zaun, puts you in it on a bad day.
The Gray rolls through the streets, welcoming me back. Most days, it’s thin enough that you can breathe deep without coughing up something wet. Today, though, is what we call a Grayout. You choke with every breath. Your chest feels tight. Can’t see much past your fingertips.
From Riot’s short story Deep Breath.
A Grayout is the story’s word for the worst days. On a normal day, our Atlas says, the lower city still runs on lamps.
What light does filter down passes through fumes leaking from tangles of corroded pipework, leaving residents dependent on artificial lighting, while streams of toxic runoff stagnate in the city's lower reaches.
From our Atlas entry for the Zaun Gray.
Riot’s Teamfight Tactics mini cinematic Memories of Zaun is set in the city, and the frame under it shows a lit bar counter.
Moving through that dark is dangerous, because the smoke is also cover. Our Atlas says couriers are hunted in it.
In the depths, augmented predators hunt pneuma-tube couriers through its smoke and chemtech puddles.
From our Atlas entry for the Zaun Gray.
The gray alleys have at least one hunter with a name: 
Warwick, a man turned into a monster by alchemical experiments. His biography opens on him there.
Warwick is a monster who hunts the gray alleys of Zaun. Transformed by agonizing experiments, his body is fused with an intricate system of chambers and pumps, machinery filling his veins with alchemical rage. Bursting out of the shadows, he preys upon those criminals who terrorize the city’s depths.
From Warwick’s biography.
When you cannot see the city, you have to know it by heart, and the locals charge for that. A Legends of Runeterra card called Sumpworks Map carries the line, credited to a Sump scavenger named Ajuna Lem.
“Pilties always think they know everything, but their maps only show the places we told ’em about! Nothing like local knowledge. Which you can have... for a price.”
Ajuna Lem, on Sumpworks Map. Pilties are Piltovans.
Our Atlas files three Legends of Runeterra cards under the Gray itself. The one with a line to quote is Sump Monument, a landmark card whose flavor text reads, “Deep beneath the streets of Zaun, you are what you eat.”
Card pages: Sump Monument, the second card, the third card.
The Rising Howl Is the Public Way Up
In Ensemble, Blitzcrank watches Zaun’s hexdraulic elevator carry a sump-scrapper, a busker and a gang in one cabin, and Riot’s gallery shows a public lift and a private one.
The way most of Zaun goes up is the Rising Howl, a hexdraulic elevator that runs between the city’s levels. Riot’s short story City of Iron and Glass opens on someone running to catch it.
“Hurry up, Wyn!” shouted Janke. “The Rising Howl’s on its way!”
From Riot’s short story City of Iron and Glass.
Ensemble, a Riot short story narrated by 
Blitzcrank, an automaton built to dispose of Zaun’s hazardous waste, watches one ride from outside the cabin.
Inside the cabin, the sump-scrapper and his child look on as a musician tunes his four-stringed chittarone and begins a sonorous melody. His tune synchronizes with the clacking gears and whirring machinery of the Howl. The father taps his foot to the rhythm. A beetle snaps her pincers as she scrambles away from the man’s heavy boot. A gang of chem-punks lean against the wall in soft repose, a pause so unlike their usual frenzied jaunts through the city.
From Ensemble, narrated by Blitzcrank.
A sump-scrapper salvages from the runoff at the bottom of the city. The stops called on that ride include the Boundary Markets and the College of Techmaturgy, whose tower Riot’s gallery shows rising into Piltover.
Riot’s region gallery draws two kinds of lift: a public hexdraulic descender and a private one.
Our read. A private lift means some Zaunites never share a car with a sump-scrapper, so the way up is sorted by money as well as by height.
Off the Lift, Zaunites Hitch, Climb or Take the Pipes
Vi’s biography has her hitching rides up into Piltover, Ekko’s has Zaun’s street kids climbing from the Sump to the Promenade, and Zac lives in the city’s pipes.
The people Riot writes without a seat on the lift still go up. 
Vi, a Piltover warden who grew up running with Zaun’s sump-snipe gangs, was a familiar sight in the undercity long before the badge, and her biography lists how she got around. One of the ways is “hitching rides up into Piltover aboard the hexdraulic conveyors,” riding the city’s machinery without being one of its passengers.
Ekko’s biography describes the way up on foot. The street kids he grew up with, the “Lost Children of Zaun,” spent their days on “foot races through the border markets, or daring climbs from the Sump to the Promenade.” The Promenade is Zaun’s top level, so that is the whole height of the city, bottom to top, by hand.
Zac, a living mass of chemicals, does not need a lift or a handhold. He was born at the bottom of the city and moves through its plumbing.
Zac is the product of a toxic spill that ran through a chemtech seam and pooled in an isolated cavern deep in Zaun’s Sump. Despite such humble origins, Zac has grown from primordial ooze into a thinking being who dwells in the city’s pipes, occasionally emerging to help those who cannot help themselves or to rebuild the broken infrastructure of Zaun.
From Zac’s biography.
Hitching and climbing take nerve, and the pipes take a body like Zac’s. Everyone else stays below and lives with the air.
Zaunites Who Stay Below Breathe Through Machines or Pray for Wind
Our Atlas says some Zaunites wear augments to breathe the Gray, and Janna’s biography says those fighting for breath trust her not to abandon them.
If you cannot get above the Gray, canon gives you two answers. The first is to carry your air with you.
For Zaunites the Gray is inescapable. Prolonged exposure causes respiratory illness, and many residents fight simply for breath amid the toxic clouds. To survive, some turn to mechanical augments that let them breathe the poisoned air.
From our Atlas entry for the Zaun Gray.
Riot’s region gallery draws the kit: a Gray-helm for a Sump breather, reusable esophilters, and an exo-philtrator built into the body. Each one lets its wearer move through air they could not otherwise breathe.
The second is to ask the air to move. 
Janna is the wind goddess our Atlas says Zaun’s faithful pray to, and her biography opens on what that faith is.
Since ancient times, there have been those who prayed to the winds. From sailors seeking good weather to the downtrodden calling on winds of change, mortals have placed their hope in the tempests and gales that sweep across Runeterra.
From Janna’s biography.
The bluebird is an old sign of her faith. Her biography says that when an emperor ordered her statues torn down, many kept praying to her quietly, and “these mortals often wore amulets with the image of a bluebird.” Our Atlas says Zaun’s faithful still wear bluebird medallions and pray for her winds to cut the smoke. Her biography says what they expect back.
And through it all, Janna stands steadfast by the humble and the meek. Zaunites all know that whether they fight for breath amid the toxic clouds of the Zaun Gray, stand against the brutality of violent chem-barons, or fend off other threats, Janna will not abandon them.
From Janna’s biography.
The narrator of Deep Breath is one of them. During his Grayout he has a wooden bluebird pendant his mother gave him, and he talks to Janna, quietly.
Not out loud, of course – don’t need people thinking I’m some chem-burnt freak – but still, I talk to her.
From Deep Breath.
Gear lets people live inside the Gray. Janna’s faithful pray for a wind that moves it.
The Top of the Climb Is Piltover, Lit Above the Gray
Riot’s gallery puts the Promenade beside Piltover’s lower districts, and our Atlas says Piltover’s richest streets are lit bright enough to pierce the rising Gray.
The climbs in Ekko’s biography end at the Promenade, and the Promenade sits right under Piltover. Riot’s gallery text says who gathers there.
The upper reaches of Zaun exist alongside the lower districts of Piltover, though the differing architecture means the two could never be confused. This is where the wealthy of Zaun gather to shop, dine, and trade goods and supplies from below.
Riot’s region text for Zaun: Promenade Level, shown below.
Above the Promenade is Piltover, and our Atlas ends its entry on the Gray there.
Above it all, the richest streets of Piltover install lights bright enough to pierce the rising Gray, a reminder that the City of Progress is paid for in the air its sister city breathes.
From our Atlas entry for the Zaun Gray. The lights are the subject of Riot’s gallery entry Piltover: Lighting the City of Progress, shown below.
The Gray rises from the bottom of Zaun. The Rising Howl, the hitched rides and the climbs all run up through it, and at the top Piltover lights its richest streets above the smoke. That trip, from the factories to “the wealth and opportunities of Piltover,” is the one Inna and Wyeth wanted for Ekko.
What This Means for the Riot MMO
Nothing about the Riot MMO is announced. Our read: Zaun is a place you cross by climbing, and its travel already has stops, a private car and a weather event.
Riot has shown no zone, mount or travel system for its MMO. If it builds Zaun from this canon, the travel is already designed, and it runs up and down rather than across.
- Height is progress. The Sump at the bottom, the Promenade at the top and Piltover above it are steps in one column, and the air at each step tells a player how high they are.
- The Rising Howl is the flight path. A public elevator with called stops, the Boundary Markets and the College of Techmaturgy among them, is a travel network you ride with the rest of the city, a sump-scrapper and a busker in the same car.
- A private car exists. The gallery’s private descender beside the public one reads to us as a paid route that skips the crowd.
- Off-lift routes cost nerve. Hitching like Vi, climbing like the street kids in Ekko’s biography, or buying a route from a local like Ajuna Lem are the ways up without a seat on the lift.
- A Grayout is weather. A day when you cannot see past your fingertips cuts sight lines in the lower levels, where our Atlas already has predators hunting couriers through the smoke.
- Breathing gear is a travel item. A Gray-helm or an exo-philtrator is what lets someone stay below the smog for long, which makes it closer to a pass than to armor.
Our read. Mounts make sense on open ground, and Zaun is a canyon of stacked levels where canon moves people by lift, by hand and by pipe. A Zaun where the elevator does the job of a mount, and the Gray is the reason to ride it, would match what Riot already wrote. It also changes how big the place feels: Zaun’s distances are vertical, so a small spot on the world map can hold a long trip.
Whose Smog Is It?
Is the Zaun Gray Piltover’s doing or Zaun’s own?
Read Next
More Runeterra canon read for the systems it already describes.
None of this is confirmed and nothing about the Riot MMO here is announced. Sources: our Atlas entry for the Zaun Gray and The Sump; the biographies of Ekko, Camille, Skarner, Warwick, Vi, Zac and Janna; Riot’s short stories Deep Breath, City of Iron and Glass and Ensemble; Riot’s Zaun and Piltover region galleries; and the Piltover and Zaun cards quoted above. A RuneGrove lore read.
