Deep Nether

The Nether is no longer another dimension. It's right under your feet.

Deep Nether moves the Nether directly beneath the Overworld. There are no portals and no loading screens. Bedrock is gone, and the bottom of the world is now a layer of obsidian. Mine through it and you break into the ceiling of the Nether, with its lava ocean, crimson forests and bastions spread out below you.

It's a pure datapack. It runs on the server, so vanilla clients can join without installing anything.

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How it works

Height	What's there
y 319 to −59	The normal Overworld, unchanged
y −59 to −70	Obsidian layer, replacing bedrock. It's at least 2 blocks thick, and you need a diamond pickaxe.
y −65 to −192	The Nether, a full 128-block-tall Nether
y −192	Bedrock floor, the true bottom of the world

The world's minimum height is extended from −64 down to −192 to make room.

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Features

Everything works like in vanilla, except following things:

No more portals

Nether portals are disabled the first time the pack loads, using the gamerule allow_entering_nether_using_portals. To get to the Nether, you dig.

Advancements, adjusted

Advancement	New requirement
We Need to Go Deeper / Nether tab	Reach a Nether biome below the obsidian
Subspace Bubble	Travel 875 blocks through the Nether in one trip. This is the same effort as the vanilla 7 km in Overworld terms.
Uneasy Alliance	Kill a ghast above the obsidian, meaning you brought it up to the surface
Feels Like Home	Ride a strider 50 blocks on lava above the obsidian

All other Nether advancements work as in vanilla.

The Overworld is untouched

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Installation

⚠️ A new world is required. World generation changes only apply to newly created worlds.

Singleplayer: Create New World → Data Packs → drag the zip in → create the world.

Server:

1. Choose a new world name (level-name in server.properties), or move the old world folder away.
2. Create the folder <level-name>/datapacks/ and put the zip inside.
3. Start the server.

Supports Minecraft Java Edition 26.3.

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Differences from vanilla and known limitations

• No 1:8 travel shortcut. The Nether layer is at the same scale as the Overworld, so it isn't a fast-travel network.
• Fortress layouts are close to vanilla, not identical. The vanilla fortress generator is hardcoded to its height, so the vanilla pieces are joined with jigsaw pools tuned to match vanilla fortresses (about 120 pieces and 200 blocks across on average). Sizes vary a little more than in vanilla, and the far ends of very long castle corridors stop sooner.
• Nether fossils are decorations, not a structure. /locate structure minecraft:nether_fossil won't find them.
• Lava flows at Overworld speed in the Nether layer. The game only allows fast lava for a whole dimension.
• It's darker than the real Nether. The Nether's constant dim glow is set per dimension, so the layer is lit only by lava, glowstone and fire. Bring torches. Sunlight can also shine down into the Nether through shafts dug from the surface.
• The cave layout is not identical to vanilla. The overall shape is close to the vanilla Nether, with similar caverns, open space and lava ocean, but it's generated differently. The Nether's narrow carved tunnels aren't included.
• Strongholds can generate partly inside the Nether layer, because the game places them anywhere between the world bottom and sea level. Eyes of ender still lead to them. Mineshafts that would land in the Nether are skipped, and their frequency is raised slightly to compensate.
• The Nether layer counts as the Overworld for compasses, clocks, maps and mob caps. Compasses and clocks work down there.
• Default world type only. Amplified, Large Biomes and other world presets are not supported.
• Incompatible with other datapacks or mods that change Overworld terrain generation, the Overworld's height, or the Nether biomes.
• New chunks can take longer to generate, because every chunk contains both an Overworld and a Nether section.
• The original Nether dimension still exists but can't be reached without commands, and its decoration is stripped.
• Ruined portals still appear in the Overworld as decoration, but portals can't be used.