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Undertale Yellow Overview

What's the Undertale game?

For those unfamiliar with the original, Undertale is a role-playing game created by Toby Fox, released in 2015. The game is known for its unique blend of humor, adventure, and emotional storytelling. Players take control of a child who has fallen into the world of monsters and must find their way back to the surface. Undertale's innovative combat system allows players to spare monsters instead of fighting them, leading to multiple endings based on their choices.

Undertale Yellow - a fan-made prequel game

Undertale Yellow takes place before the events of Undertale, focusing on the characters of Gaster and Sans. The game explores their relationship, motivations, and roles in the Underground before Frisk's arrival.

Undertale Yellow's Development

The development of Undertale Yellow began in February 2016, after Toby Fox greenlit the project. A demo was released on Game Jolt in March 2016, allowing players to experience a portion of the story and gameplay. The full game was finally released on December 9, 2023, after 7 years of development and anticipation.


Undertale Yellow Feature

Game Story

Undertale Yellow picks up before the events of the original Undertale, focusing on the enigmatic characters Gaster and Sans. The story delves into their past, exploring their relationship and the events that shaped their lives. Players will uncover secrets about the Underground, the Royal Family, and the enigmatic Gaster.


Undertale Yellow retains the core gameplay mechanics of Undertale, including turn-based combat and the Fight-Spare system. However, it also introduces new elements, such as:

  • New puzzles and challenges that require players to utilize their creativity and problem-solving skills.
  • Enhanced combat system with improved mechanics and new enemy types.
  • Unique areas and environments to explore, offering players a fresh perspective on the Underground.

Game Rule

As in Undertale, player choices have a significant impact on the story and the fate of characters. By choosing to fight or spare monsters, players can influence the course of the game and unlock multiple endings.

Undertale Yellow's Characters

Undertale Yellow features a mix of familiar faces from the original Undertale, alongside completely new characters that enrich the lore and expand the world. Here's a closer look at some of the key characters you'll encounter in the game:

Main Characters:

  • Clover: The protagonist of Undertale Yellow, a curious and kind child who falls into the Underground. Unlike Frisk, Clover possesses unique abilities that influence the story and gameplay.
  • Dalv: A mysterious figure who appears to mentor Clover and guide them through the Underground. Dalv's true motives and origins remain shrouded in secrecy.
  • Ceroba: A determined and skilled monster warrior who serves the Royal Family. She becomes an ally to Clover and helps them navigate the dangers of the Underground.
  • Starlo: A young and optimistic monster child who befriends Clover. Starlo's innocence and purity stand in stark contrast to the harsh realities of the Underground.

Returning Characters:

  • Flowey: The mischievous and enigmatic golden flower returns in Undertale Yellow, playing a pivotal role in the story.
  • Toriel: The caring and compassionate goat monster who initially encounters Clover. Despite her kindness, Toriel harbors dark secrets and regrets from the past.
  • Snowdin: The skeletal brothers return in Undertale Yellow, offering comedic relief and philosophical insights. Their role in the story is still being revealed.

New Undertale Yellow Characters:

  • Martlet: A nervous and anxious bird monster who helps Clover navigate the ruins. Martlet's knowledge of the Underground proves invaluable to Clover's journey.
  • Micro Froggit: A tiny frog monster with a big personality. Micro Froggit's playful nature and optimism provide a lighthearted counterpoint to the game's darker themes.
  • Gaster: The enigmatic scientist who disappeared before the events of Undertale. In Undertale Yellow, players will finally learn more about Gaster's past, his motivations, and his impact on the Underground.

Undertale Yellow offers a compelling cast of characters with unique personalities, motivations, and backstories. Each character plays a vital role in the story, enriching the world of Undertale and providing players with a deeper understanding of the events that unfold.

How to play Undertale Yellow?

Undertale Yellow is currently available in 2 PC versions: The online version and the DLC Undertale Yellow Game Jolt.

Play Undertale Yellow online

Game Instructions:

  • [Z] - Confirm
  • [X] - Cancel
  • [ARROW KEYS] - Move SOUL
  • [Green flag] - RESET
  • When HP is 0, you lose.

Play DLC Undertale Yellow Game Jolt

To play the game, simply:

  • Visit the game's official page:
  • Click on the "Download Game" button.
  • Choose the appropriate download option for your operating system.
  • Once downloaded, unzip the file and run the game executable.

Before playing Undertale Yellow, it is recommended to play the original Undertale for a richer understanding of the story and characters. However, the Undertale Game can still be enjoyed as a standalone experience for fans of RPGs and narrative-driven games.

Undertale Yellow offers players a chance to revisit the beloved world of Deltarune from a new perspective. With its intriguing story, engaging gameplay, and challenging choices, it is a must-play for fans of the original and RPG enthusiasts alike. So, embark on a journey through time and explore the secrets of the Underground before Frisk's arrival.

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