Install the Aether mod on your server

The Aether adds a dimension high in the sky, with floating islands, new ores, new mobs and three dungeons, each with a boss. It is the original Aether mod, kept up to date by the Aether Team. It is needed on the server and on every player's game.

Checked against The Aether 1.5.10 on NeoForge 1.21.1, October 2026.

Pick the server version

Modrinth lists The Aether 1.5.10 (28 September 2025) for NeoForge on Minecraft 1.21.1. A Fabric 1.21.1 build, 1.5.11, also exists. The NeoForge jar's mod file asks for Minecraft 1.21.1 exactly and NeoForge 21.1.72 or newer. The panel installs the newest stable NeoForge build for the version you pick, which is well past that minimum.

Open JAR Manager under More, set Server software to NeoForge and Minecraft version to 1.21.1, then press Apply change. Leave Take a backup first ticked, then press and hold Confirm & reinstall for 3 seconds. The panel picks Java 21 for you. Change your Minecraft version or mod loader has the full steps.

What it needs

The jar carries Cumulus, Accessories and Nitrogen inside itself, so you do not install those. The Accessories copy it bundles asks for oωo (owo-lib) 0.12.15 or newer, and Modrinth lists owo-lib as required. The owo-lib builds for NeoForge 1.21 are marked beta.

Install it

1. Open Mods under Content. The Modrinth chip is selected by default, and the Game version filter starts on your server's version.
2. Search for The Aether and choose the one by Katie-Payn. Add-ons such as "The Aether: Redux" appear too, and they are different projects.
3. Press Install. When the "Needs" window appears, press Install all so owo-lib comes with it. If it does not appear, search for owo-lib and install the newest NeoForge 1.21 file.
4. Restart from the Console tab.

Open the Installed view afterwards. Both mods should show with no Failed to load badge.

Players need it too

Each player installs The Aether 1.5.10 and owo-lib for NeoForge 1.21.1. Join a modded server from your launcher covers the player side, and Fix the missing mods exception when joining helps when a player is refused.

Getting into the Aether

The mod page says the portal is built from a Glowstone frame and lit with a water bucket in the middle. Stepping through takes you to the dimension. If you fall off an island you end up back in the Overworld. The Aether has Eternal Day, which only ends once the Gold Dungeon is conquered. After that the Sun Altar controls the day cycle.

Server settings

After the first start the config folder holds aether-server.toml, aether-common.toml and aether-startup.toml. The serverconfig folder inside your world folder only holds a readme.txt. Stop the server before you edit either in the File Manager. Keys the jar defines:

• Disables Aether Portal creation (false) stops players building the portal.
• Disables eternal day (false) gives the Aether a normal day cycle straight away.
• Spawns the player in the Aether (false) starts new players in the dimension.
• Balance Invisibility Cloak for PVP (false) is aimed at PvP servers.
• Gives player Aether Portal Frame item (false), in the common file, hands out a portal frame item on world creation.

Common problems

• The server stops at startup: open the Console. The Accessories copy bundled in the jar lists owo-lib as required, and the mod file asks for NeoForge 21.1.72 or newer, so check both first. Fix mod and plugin errors on Minecraft covers reading the log.
• The mod is missing from the store: the Game version filter follows your server. The NeoForge build exists for 1.21.1 only.