Installation

Vortex Dread is a Fabric mod and it goes on both sides: on a server it decides the weather and the destruction, on a client it draws the funnel and plays the roar. Single player, the same jar does both. The Minecraft version and the loader version the jar expects are written on the download page, which is the only place kept current; check there before downloading rather than trusting what is written here.

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Neither platform carries the mod yet. Until they do, the jar comes from the repository's releases page, github.com/Dreyka-Oas/VortexDread/releases, and the two buttons above light up the day those pages exist.

Four steps

Install Fabric Loader 0.19.3 or newer on Minecraft 1.21.11, and Java 21 if your launcher does not bring its own.
Get Fabric API, which is a hard dependency: without it the mod refuses to load and says so.
Drop the jar into .minecraft/mods on a client, or into mods/ at the root of a dedicated server. Nothing to configure in order to play: the options file writes itself on first boot.
If another mod already redraws the weather, set rebuildStorms to false before launching, or the two will paint the same sky independently. See the compatibility page.

Nothing is blocked at boot. The mod declares no incompatibility in its manifest and never refuses to start because of a neighbour. That choice has a cost: two mods that take over the look of a thunderstorm will sit side by side with no error and produce something ugly, and nobody will warn you. The symptom is visual, it shows up only during a storm, and it is fixed with one boolean rather than by uninstalling anything. The detail is on the compatibility page.

Dedicated server with no graphics card. The mod looks for an OpenCL device at boot, and finding none it falls back to a thread pool on the processor that answers with exactly the same numbers. Nothing to install on the host: the natives travel inside the jar. One log line says which of the two paths took the work. See the page on compute.

Licence

The mod is MIT, and the full text travels with it under the name LICENSE. That text is what counts. The summary below has no legal weight whatsoever, it is here to answer quickly the question everyone has before reading three paragraphs of American law.

Play it and share it: single player, on a public server or inside a modpack, without asking anyone.
Change it and republish it: fork, patch, derivative version, including inside a paid project.
The one obligation: keep the copyright notice and the licence text with any substantial copy of the code.
What is not promised: the mod comes as it is, with no warranty of any kind, and the author answers for nothing that happens to your world.

Taking the code. There is no permission to ask, not for an addon, not for a fork, not for copying a piece you like. A mention in the description is welcome and has never been a condition. What is stable and what is not is written on the page for addon authors.