Wield the Ring: A WotR fan made variant.
So I've done some looking around and haven't found anything anywhere where people have played with the idea of using The One Ring against Sauron in a game variant. Yes, this is folly, surely the ring would betray almost any master aside from Sauron. Even if you beat Sauron, he would eventually return because the ring is still there. The new Wielder would eventually be betrayed anyways as Isildur was or outright become corrupted, using the power for dark purposes...
All the same, I think it could be a fun variation to try creating!
This is a write up of the rules which is just a first pass and will almost certainly need more balancing. I went with the idea that out of the companions present, only a few could actually Wield the One Ring to any real effect: Boromir, Strider (and Aragorn), Gandalf, and Galadriel.
Each gets their own kind of benefits and will have to deal with the risk of corruption going forward. It also means the FP player must reach 6 VP for FPMV rather than 4 (I did this to avoid someone just declaring a wielder to quickly take a second SH and win) or the Wielder must go to Barad Dur and confront Sauron themselves, a challenge with significant risk.
The Wielder must stay with an army at all times so that their actions can be contested by the SP. (I fear an untethered Companion would have too much leeway for any counterplay)
Again all this likely would need some serious balancing, but it was fun putting together a first pass that tries to match the concept. Please give any feedback you'd like!