I had this idea a few hours ago. Suppose there was an NPC in Britain called a "Monster Hunter".
Edit: Or maybe it could warp randomly between the inns of the world

A spawn would be set up in Felucca for a new type of monster called a "Fiend". The fiend has a random chance of being one of several different types of fiends...ice, fire, poison, energy, and steel. These would be incredibly strong monsters with new attacks I would script. They could spawn anywhere in Felucca outside of a dungeon, but only one would spawn at a time, and there would be some downtime between spawns. (this also means no ankh nearby, so fighting one alone would be stupid)
You would talk to the Monster Hunter to buy a "Magicked Stone of Tracking" for a significant price(helps the economy...100k per stone would be a good price.) which you could use every thirty seconds to get a rough direction of where the monster currently is. There could also be a max number of uses on it, such as 5-10, and you'd have to find the fiend before the stone broke (causing you to have to return to Brit to buy another one). You'd also only be able to carry one stone at a time. Anyone with a stone on their person could attack the fiend, which would of course be much too strong for any one player to take down, and anyone without a stone could not attack it or be attacked by it. And to make it worthwhile, the fiend would have drops with a possibility of high bonus dropped weapons, as well as a 10% chance to get one of the following: a significant random number of oints(20-50), a significant random number of organics(500-1000+), or one of the special artifacts I would design to come with the fiends.
Does that sound like something we could do? I think it would be a good way to teach myself C# to design something like that.