Ring War, Velious era, Coldain Prayer Shawl type of event....
Definitely -not- a solo undertaking, not quite sure how many players would be the optimal number.
...but have it be Players vs. Satan Clawz' evil elves. And yes, I'm suggesting an evil cat-type creature for one of the villains.
And for a solo-player, someone mentioned the 12 Days of Christmas collection idea, that actually sounds like it could be a ton of fun.