1.21-1.4.0 is a release file of the Minecraft mod Underground Biomes for NeoForge, made for Minecraft 1.21.1. It was published on August 23, 2026 and is 3 MB in size. For the full description, screenshots and every other version, visit the Underground Biomes mod page.
How to install: Put the .jar into the mods folder (.minecraft/mods) and start Minecraft with the matching mod loader profile.
