It is kind of hard to put the Tolkien Rings of Power into D&D terms, but I have always wondered if it could be done in a game like BG III. Here is what I got so far for the Ruling Ring:

- Move about unseen.
- See the unseen.
- Know the thoughts of the other Ring wielders.
- Spread fear.
- Plant suggestions, to bend other minds to the Ring's will.
- Everlasting unlife.
- Addictive behavior upon its wielder, for it is ... precious.

Is that about it? I guess most of those could be covered by D&D magic ... mostly 1-3 level spells. Something seems missing.