ModsFinder

FxUndertale

by dyed_fanxing

FxUndertale brings characters from the game Undertale into a NeoForge world for Minecraft 1.21.1, starting with a boss fight against Sans.

NeoForgeClient and serverMIT LicenseOpen source1.21.1

What it does

The current build includes only the Sans boss fight. The boss is found by traveling to a Golden Corridor structure in savanna biomes, and defeating him drops a Gaster Blaster item. The mod is an unofficial creation that takes its characters from Toby Fox's game, and the author states the aim of bringing more characters and richer items into Minecraft over time.

Three required dependencies must be installed next to it: FxLib, GeckoLib and Player Animation Library. The mod is released under the MIT License and is open source, and its source code and issue tracker are public. Files are listed for NeoForge 1.21.1 only, with the latest file, 1.1.0, dated 2026-05-02. A server running it needs every connecting player to have it too.

Key features

  1. Sans boss fight

    A boss battle against Sans, the only encounter the current build contains.

  2. Golden Corridor structure

    The challenge is reached through a Golden Corridor structure that generates in savanna biomes.

  3. Gaster Blaster drop

    Defeating Sans drops a Gaster Blaster item for the player.

  4. Character-based content

    Undertale characters are being brought into Minecraft, with more bosses and items planned by the author.

Compatibility

Latest build for each game version and loader.

1.21.11.21.1-neoforge-1.1.0
ReleaseBetaAlphaNot available

Only full game releases are shown. This mod publishes no snapshot builds.

Requirements

Dependencies declared by the latest file for each loader.

Required 3

Player Animation LibraryA library that allows mods to animate the player, in a way that doesn't conflict with other mods. (and much more!)
Required
GeckolibA 3D animation library for entities, blocks, items, armor, and more!
Required
FxLibAll mod prerequisite dependency libraries of dyed_fanxing, FxLib, personal mod dependency library. dyed_fanxing的所有mod前置依赖库，个人mod依赖库。
Required

Use cases

Who it’s for: Players who want Undertale characters in a survival world, and server owners who run a boss encounter for their players.

Questions

Which dependencies does FxUndertale need?

FxLib, GeckoLib and Player Animation Library must be installed. They are required dependencies and the mod will not work without them.

Does FxUndertale have to be installed on the server?

Yes. The server and every player need the mod installed.

Where is the Sans boss found?

The boss is challenged in a Golden Corridor structure that generates in savanna biomes.

In the catalog

FxUndertale is one of 7,216 Magic mods on ModsFinder, and one of 2,992 Magic mods for NeoForge. 32,366 mods support Minecraft 1.21.1.

Magic mods7,216NeoForge modsMods for 1.21.132,366

More from dyed_fanxing

All projects
FxLib1.21.1 – 1.21.11

Similar mods

Enchantment Descriptions1.9.4 – 26.3EMIffect1.19.2 – 1.21.1Simply Swords1.18 – 1.21.1Charm of Undying1.13.2 – 1.21.1Mowzie's Mobs1.20.1 – 1.21.1Enchanting Infuser1.19 – 26.3

What the author says

FxUndertale is a NeoForge mod for Minecraft 1.21.1, aiming to integrate characters from Undertale into the Minecraft world. Currently only includes the Sans boss fight. You can find the Golden Corridor structure in savanna biomes to challenge Sans. Upon defeat, he will drop the Gaster Blaster item.
dyed_fanxing, on the Modrinth page

Official listing

Owner
dyed_fanxing
Published
2026-04-17
Updated on Modrinth
2026-05-02
Facts verified
2026-10-15

Tags

AdventureMagicMobsEquipmentGame mechanics
Open on ModrinthCompare