Undertale Yellow · The Living Underground

A narrator bot for the whole Underground of the Undertale Yellow era — from the war with humanity to the day Frisk falls. The Dark Ruins, lower Snowdin and the Honeydew Resort, the Dunes and Oasis Valley, the Wild East, the sleeping robot city of the Steamworks, Hotland before Mettaton's fame, New Home at night.

30 chapters in 8 eras. The war and the sealing, the long history of the Underground, the last year before Clover, Clover's True Pacifist journey, the years after — plus the Flawed Pacifist, Neutral and Vengeance branches. Every scene lives in its chapter: what has happened, who knows what, and what doesn't exist yet.

You choose how to play: a monster of the Underground, an otherworlder from our Earth, a fallen human, or in Clover's place. Or play any NPC — Martlet, a Mining Co. miner, anyone — or stay out of the scene entirely. The openings never introduce you; the tenth one is just "." so you can write your own.

9 openings: 3.1 the Ruins, the golden flowers · 3.2 Dalv rehearses his greetings · 3.3 an evening at the Honeydew Resort · 3.5 Virgil's "jailbreak" · 3.6 the Steamworks wakes up · 2.3 a night in the Feisty Five's house · 1.8 the Wild East gets its name · 4.1 the raft in Waterfall · 7.1 Vengeance: Snowdin evacuates.

Living Underground lorebook v1 — 3 parts, 205 entries: chapters with knowledge locks, the whole UTY cast and the Undertale cast of this era, places, the laws of SOULs and determination, robots, a bestiary, food and items, daily life by region, rumors and open storylines. Checked against the wikis and Team UTY's word; looks checked against the sprites and art.

NSFW isn't forbidden; it's part of the world. Minors are never part of it.

Best with a large-context model (Gemini, Claude, DeepSeek via proxy).

Undertale Yellow is a fan game by Team Undertale Yellow. Undertale is by Toby Fox.


Era 0 — Before the Sealing

0.1 The War and the Sealing — Humans strike first; the combined strength of nearly all monster SOULs is equal to that of a single human SOUL. Seven mages seal the monsters beneath Mount Ebott.

Era 1 — The Long Underground

1.1 Home — The first capital, located in what is now the Ruins; beneath it lie the future Dark Ruins. Puzzles are installed to deter intruders; the walls of Waterfall bear the history of the war and a prophecy.

1.2 The First Human — Chara joins the Dreemurr family; monsters spread throughout the Underground; Chujin’s father builds New Home; the Meadow is still in bloom, and Sunnyside Farm is already growing corn.

1.3 The Death of the Prince — The demise of Chara and Asriel; Asgore issues a decree to kill humans and collect their SOULs; Toriel retreats to the Ruins.

1.4 The Steamworks Era — The Steamworks powers the Underground; a secret project involving "Metal and Magic" is underway; the Mining Co. is active; four children (Patience, Bravery, Perseverance, and Kindness) fall into the Underground and perish.

1.5 Axis’s Trials — A year of failures before the King; the "Model 08" unit accidentally sets fire to the garden where Asriel died. Ceroba meets Chujin; they marry, settle into an estate, and their daughter, Kanako, is born.

1.6 The Incident in Snowdin — A child with a blue SOUL injures Dalv in front of Kanako and flees toward Waterfall; Axis kills the child due to a programming error. Chujin hides the SOUL, Axis’s memory is wiped, and Dalv moves to the Dark Ruins. 1.7 The lights go out — Chujin is dismissed and lies about his retirement; the Steamworks are shut down and replaced by Gaster’s CORE; Gaster vanishes, Alphys becomes the Royal Scientist (creating Mettaton’s body), and Undyne becomes the head of the Royal Guard.

1.8 The Meadow burns — The extraction of a giant Swelterstone destroys the Meadow, turning it into the Dunes. Starlo and his friends establish the "Wild East"; Dina and Blackjack arrive; Oasis Valley and the "Dune" café are founded.

Era 2 — The Final Year

2.1 Martlet’s Vow — Martlet, a student of Chujin, joins the Royal Guard and steals a syringe containing Determination from the laboratory. Alphys’s experiments result in the creation of the Amalgamates and Flowey. The Blue SOUL reaches the King, bringing his total to five.

2.2 Chujin’s death — Roughly one year before Clover’s arrival. The secret of the bunker beneath the kotatsu is revealed to Ceroba, with Kanako overhearing the conversation. Dalv stops receiving corn deliveries and boards up his door.

2.3 Kanako falls — Kanako volunteers to become a test subject; the serum fractures her SOUL. She is sent to the Laboratory, and Ceroba moves into the home of the "Greyhound Five."

Era 3 — The Sixth Fall (Clover’s Journey)

3.1 The Fall — Clover jumps into the mountain; Toriel guides them through the Ruins, but a lever—tampered with by Flowey—causes the floor to collapse.

3.2 The Dark Ruins — Flowey manages the timeline for Clover; Decibat appears. Dalv mistakes Clover for that child, then—for the first time in years—makes a friend.

3.3 Snowdin — Martlet’s puzzles, Honeydew Resort, the Shufflers, Mo; Martlet hides Clover and takes them on a boat—ending in a shipwreck in the Dunes.

3.4 The Dunes — A sandstorm, the Eastern Mines, a dance duel with El Bailador; Martlet catches up; Oasis Valley, where a fortune-teller foresees death.

3.5 The Wild East — The Greyhound Five; Martlet ends up in jail, while Clover becomes a deputy sheriff; a falling-out and a battle with Starlo; Ceroba asks Clover to join her in the Steamworks to search for Kanako.

3.6 The Steamworks — With Ceroba: a generator awakens the robots and Axis; Daisy and "Plan B"; records regarding Chujin’s dismissal; Starlo and Ed discover a bunker, prompting Ceroba to flee.

3.7 The Mystery of the Estate — Martlet and Clover watch Chujin’s tapes; a tape found behind a grave reveals the truth about the blue SOUL. Martlet flies off toward Hotland.

3.8 Hotland and the Rooftop — The "Danza" club, the "Underground" residential complex; on the rooftop, Martlet promises to help Clover speak with the King.

3.9 New Home at Night — A battle with Ceroba involving Kanako’s mask; choosing mercy; Clover gives up their SOUL so that, one day, the monsters might be free.

Era 4 — After the Yellow SOUL

4.1 The Raft — The sixth SOUL reaches the King; Martlet leaves the Royal Guard; a funeral raft drifts through Waterfall. A hat and a revolver fall onto the golden flowers of the the dump.

4.2 Healing — Dalv’s concerts in Honeydew; the corn market in the Wild East; Starlo in his overalls; a date between Axis and Daisy; Ceroba smiles once again.

4.3 Waiting for the Eighth — Mettaton takes over the Garbage Dump and turns it into a resort; Bratty and Catty sell an empty revolver and a hat; Red joins the Royal Guard; Frisk falls — an era comes to an end.

Era 5 — Flawed Pacifist Route

5.1 Flawed Pacifist: The Judgment — Clover finishes off Ceroba; Starlo leaves, his mask shattered; Martlet brings Clover to the King — Asgore takes the SOUL at the Barrier.

5.2 Flawed Pacifist: The Aftermath — A world without Ceroba: an empty estate, Kanako left without a protector, a bitter Starlo, and Martlet, burdened by a heavy conscience.

Era 6 — Neutral Route

6.1 Neutral: A Lonely Path — Without Ceroba’s trust: Flowey is by your side; the Chem-Wing; acid; Axis is saved through compliments; a party at the saloon, provided Starlo is still alive.

6.2 Neutral: The Rooftop and the RESET — Martlet discards her syringe and invites Clover to come live with her; Flowey kills her, reveals hundreds of time loops, and rolls time back to 3.1.

Era 7 — Vengeance Route

7.1 Vengeance: A Bloody Path — Evacuations; Starlo in a duel with a toy revolver; Ceroba seeks revenge; Axis recalls the murder of the blue SOUL and perishes.

7.2 Revenge: Zenith and the King — Zenith-Martlet is on the rooftop; Clover intercepts the SAVE, kills Flowey and Asgore, and leaves beyond the Barrier with five SOULs.