Deep Underground (Mining Dimension)
by Bluestar_
Deep Underground is a Fabric world generation mod that adds a 256-block tall deepslate cave dimension reached through a custom portal.
What it does
Deep Underground adds a cave dimension made of deepslate that reaches 256 blocks in height. To open its portal, a player needs at least 10 framed polished blackstone blocks, lit with a lava bucket. Coal does not generate in the dimension, so ore has to come from elsewhere. Additional ores and structures can be added through external datapacks.
The mod is built around deeper mining. Viridium and Cerulium are found further down in the dimension, and gear made from them is used for the deeper levels. Since 1.1.0, Cyclite fuel for furnaces rarely generates as ore, and it is found in rare geodes.
Deep Underground runs on the client and the server, so both sides need it. It is published for Fabric only, for Minecraft 1.21.1, with 1.1.0 as the latest file, released on 2026-03-25 under the MIT License. The source code and issue tracker are public.
Key features
Deepslate cave dimension
A 256-block tall cave dimension made of deepslate, reached through a portal in the overworld.
Blackstone portal
The portal is lit from a frame of at least 10 framed polished blackstone blocks, using a lava bucket.
Deep ores and gear
Viridium and Cerulium are mined deeper in the dimension and crafted into armor and tools.
Depthbound Steel
Cerulium is used to make Depthbound Steel, which comes from an Inert Depthbound Block placed below Y=24.
Cyclite fuel from geodes
Since 1.1.0, Cyclite fuel for furnaces is rarely found in rare geodes instead of as common ore.
Gallery
Compatibility
Latest build for each game version and loader.
Only full game releases are shown. This mod publishes no snapshot builds.
Required by 1 mod
Use cases
Who it’s for: Players who want a mining-focused progression on Fabric for Minecraft 1.21.1, and server owners who plan to run custom ore datapacks alongside the mod.
How it compares
Ethrilic Dimension is a Fabric server-side only mod for 1.21.8 – 1.21.11, under All rights reserved and not open source, so players can join without installing it. Deep Dark Expanded is a Fabric client and server mod for 1.21.11 under the MIT License, and it is open source. Deep Underground covers only 1.21.1 and needs the client and server.
| Mod | Loaders | Game versions | Environment | Updated |
|---|---|---|---|---|
| Deep Underground (Mining Dimension) | Fabric | 1.21.1 | Client and server | 2026-03-25 |
| Ethrilic Dimension | Fabric | 1.21.8 – 1.21.11 | Server-side only | 2026-04-11 |
| Deep Dark Expanded | Fabric | 1.21.11 | Client and server | 2026-01-14 |
Questions
Does Deep Underground need another mod to run?
Does the server need Deep Underground installed?
Which Minecraft version does Deep Underground support?
In the catalog
Deep Underground (Mining Dimension) is one of 8,515 World generation mods on ModsFinder, and one of 4,027 World generation mods for Fabric. 32,366 mods support Minecraft 1.21.1.
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What the author says
To create the portal, craft at least 10 framed polished blackstone blocks, place them in a Nether portal shape and light it with a lava bucket. The dimension is very dark, and coal doesn't generate. However, additional ores and structures can easily be added with external datapacks.
Official listing
- Modrinth page
- modrinth.com/mod/deep-underground
- Owner
- Bluestar_
- Published
- 2025-05-27
- Updated on Modrinth
- 2026-03-25
- Facts verified
- 2026-10-15