Yeah, the point of my post wasnt about stat boosts or other mechanical nonsense. I couldn't care less about that. The point is the make the players want the ring, and have it bestow great power. The corruption would come from the actual players wanting the ring themselves. Instead of some stat that says how corrupted you are, I want the players to want that ring for themselves. (Or sock or pendant or whatever you want it to be). I think the stat boosts would just make the others want it that much more, each time it's stole it gets more powerful (stat boosts was just a suggestion. Perhaps the rings bestows a new power specific to a player's wants and needs) I just was thinking of a way to really make the players want that object without it being just a number on a character sheet denoting how much your character wants it.
Is it necessary that that
players have to want it? Are you doubting their ability to role-play their characters coveting the item, not wanting to relinquish it? Have they ever had to play their PC when the PC is charmed, or otherwise temporarily suppose to act against the player's interest?
I mean, the item should probably have some desirable benefit, like the One Ring's invisibility, and obviously the players would recognize the benefit to their characters, even if they know it's ultimately an evil artifact. But what if a player decides their character is going to resist temptation, despite the benefit? What if they all do? It sounds like you expect the game to devolve into Lord of the Flies based on
player motivations, but there's no guarantee that's going to happen.
The other issue is, if the item is really powerful, there's a certain type of player more likely to risk being the owner of the item, purely for the mechanical benefit. (Not to say there wouldn't be players who'd reasonably roleplay being the one to take the item, but there's a great deal more unpredictability there of it happening, unless you already know the
character likely to possess the item.) If the item is that powerful, the possessor is likely to outshine the other characters in combat or even possibly roleplaying encounters, depending on the abilities granted. You may find that rather than engendering covetousness among the other players, it may simply be annoyance with the possessor and/or the game master. "Hey, I know. Let's throw the ring AND Bob into Mount Doom."
Also, what's the end game? Are the characters suppose to go on a quest to destroy the item? If you've made the players want the item so badly, what's now going to motivate them to destroy it?
In the campaign I'm currently playing in (3.5 in a Wild West setting), half the party has picked up an intelligent, shape-shifting weapon. Each was a really good fit for our characters, but then we discovered they're part of a set of six belonging to a powerful demon, and they've been subtly encouraging us to get the full set, and to go exploring a dungeon where we now know the demon is imprisoned. It took some debate and successful Will Saves, but we're now on our way to present the items to a legendary good-aligned creature that we know will be able to destroy the items. My PC got his first at low level, and it's a +1 silvered revolver of Speed that can cast Detect Thoughts and some other abilities I haven't unlocked yet. It was a tough decision to let it go, because it was really a pretty powerful weapon, but my priest-turned-gunslinger character relinquished for the greater good.
