Please read the guide for contributing before posting.

Minecraft version: 1.12.2 [change as necessary]
Wizardry version: 4.3.1 [change as necessary]
Environment: Singleplayer/LAN game/Server [delete as necessary]

Issue details: I have curse of undeath. I've used many purifying elixirs they still don't work.

Other mods involved: [only list mods that are relevant to the problem]

Link to crash report (if applicable): [give a link to the crash report on gist, pastebin, etc.]

Old version issue. Reopen if still present in 4.3.4+

Okay, could you check the following:

1. Does the remove curse spell work?
2. If you drink an elixir and then restart the world / relog, does the effect go away?
3. Does it make a difference if you have any other potion effects?
4. Do you have any potion-related mods installed?

Working as intended in my installation. Of course, it won't put you out immediately if you're on fire.