For a fleshed out effects pack for this framework see MyGoodShades.
Should work on Hades and Pyre and hopefully Hades 2 after some minor alterations.
This will NOT work on Windows Store / Game Pass games.
You need the latest Mod Importer, Mod Utility, and StyxScribe.
(get Mod Importer from GitHub releases, and the rest by cloning the respective repositories)
For clarification, Mod Importer's content should be extracted to the Content folder, Mod Utility's content should be in a folder called ModUtil with a modfile.txt directly inside, then put that folder in Content/Mods, StyxScribe's content should be put directly into your game's top level directory, so for Hades that's just the folder Hades.game.app on macOS and Hades on the rest.
You need at least python 3.8 and you need to run Mod Importer's modimporter<.ext> (where <.ext> depends on which version you got) first, and then run the appropriate Subsume<game>.py such as SubsumeHades.py for Hades.
For modders, use the Crowd Control SDK to test effects by loading the a .cs file in Content/CrowdControlContent.
You can fork this repo and make pull requests but try to only make changes to the Packs folder.
The Base Pack contains a lot of comments that hopefully make the format clear.
For streamers, use the Crowd Control Twitch extension and the Crowd Control app to load a .ccpack file in Content/CrowdControlContent.
You may also need the Crowd Control SDK to turn a .cs file into a .ccpack, as that assigns points to the effects.