Install IronGrave

Step 1 - Get Prism Launcher

Download Prism Launcher (version 11 or newer). Install it and sign in with your Minecraft account once.

Step 2 - Install IronGrave

Prism asks you to confirm. The first launch downloads about 1.6 GB of mods, then every launch checks for updates automatically.

Link not working or older Prism? Download IronGrave.zip, then in Prism choose Add Instance → Import and pick the file (or paste this address: https://irongravemc.com/downloads/IronGrave.zip).

Good to know

Needs about 8 GB of free RAM for the game (Prism is set to 8 GB max; lower it in Edit → Settings if you have less).
Java 21 is installed automatically by Prism (Settings → Java → auto-detect and auto-download).
The IronGrave server is already in your multiplayer list (play.irongravemc.com). The game does not auto-join, singleplayer works as usual.
If a mod file gets corrupted, delete packwiz.json in the instance's minecraft folder and launch again.