A Lord of the Rings strategy game where you play as Sauron.
I've always imagined Sauron to be basically like the player in an RTS. He can see anywhere, but only in one place at a time, and can either control his units directly or give them general instructions. Your objective is to take over Middle Earth. Getting the Ring would give you access to much more powerful abilities but beyond that it would be similar to a standard RTS with a branching storyline depending on the choices you make.
To prevent the player from gaming the system by virtue of knowing what happens in the story, the Ring could potentially wind up in a number of possible scenarios, both based on RNG and also the decisions of the player impacting the AI, who is trying to keep it out of your hands. It could end up being stolen by Boromir, or used by Aragorn, or given to Galadriel, or utilized by Saruman, or thrown into the sea, or picked up by Gollum, or lost and found by some random NPC. The enemy units would make rational decisions, but the AI could also "cheat" somewhat since your enemy is Eru.
When someone puts on the Ring, you get an alert and a "hot or cold" meter would appear, depending on how far away the Ring is from your current viewing position. You can use this time to try and locate the Ring or at least get a general feel for which direction it is. You can encourage this by sending units in the general direction that you think the Ring is.
The final boss would be Tom Bombadil, who could wipe out like a hundred orcs with one attack.