The quest will be a sort of "bounty-ish", "cat-and-mouse" chase/hunt mission (or a Mad Max Fury Road chase if you like that metaphor better), where all the other ships (if they want to) on the server/map will be searching/hunting for one sloop (willingly player(s) and not npc) that contains a precious diamond (worth about 10 000 gold, that it’s trying to deliver across the map - in other words a long distance, with a huge chance to encounter other ships, that will try and stop it and steal the diamond).
Description of the quest:
The quest is just obtainable by finding it in a "message in a bottle" and by sloops only (because this quest will probably be too easy to complete for a galleon because of their speed), where one will find a map of an big outskirt island (smugglers bay, marauders arch, old faithful isle, kraken’s fall, devil’s ridge, thieves haven, discovery ridge, crescent isle or mermaid’s hideaway) with a diamond marker (instead of a X marker). If one then goes to this outskirt island (as instructed, and preferably one that you are currently closest too), one will find a castaway pirate (which wrote the message in the bottle) at the diamond marker. The castaway pirate tells you that he has been hiding on the island for many years with a precious treasure (a diamond which is “bright as a thousand star” and can be seen at both night and day - in the same manners as you spot a “message in a bottle” on the beach), which he is willing to share with you if you deliver it to an island of his choosing (randomly chooses one of the small outskirts islands that is farthest away from the island he currently is on (if picked up at i.e. smugglers bay, then the diamond has to be delivered to either one of these islands (not a choice but randomly chosen by the game in advance); Mutineer Rock, Booty Isle or Lookout Point). Delivering to outposts will probably make it too easy for other players to guess which outpost the diamond is going to be delivered to (since there are so few outposts), and therefore will possibly be camping there – the battle for the treasure needs in other words to happen on the sea, because it will be too difficult to determine where the diamond is supposed to be delivered.
The castaway is not willingly to physically let go of the diamond, and he has also lost both his legs (when the ship went down) so you have to carry him with you (while he always clings on to the diamond). He has also forgotten the name of the island, but knows the shape of it, in the same way as some gold hoarder quests (this is to prevent enemies to just run onto the boat and quickly find out where the sloop is delivering the diamond - before possibly getting killed - and camping on that island awaiting the diamond to be delivered there).
How the mechanics of the quest would work:
This quest is only attainable when the server/map is full or nearly full (so the quest won’t be too easy to complete). The quest starts when you accept the mission from the castaway pirate, and thus you can scout on forehand to see if the coast is clear (literally),and choose when it is best to accept the mission and set sail. Because at the same moment you accept it, all the players on the server/map will be informed by a message on the screen (i.e. “there are rumors of a precious treasure travelling the seas”). This message will stay on the screen (will minimize to a small recognizable icon after a minute or so – and can be shown again by going into the menu or something similar), as long as the diamond is still not delivered. And when this quest is active, other players will be able to intervene and steal this diamond (with the castaway pirate at the same time, as he will not let go of the diamond), and deliver it themselves. One can always get the information of the delivery destination from the castaway pirate (he shows a drawing of the island).
The diamond shines brightly (both night and day) and will be able to be spotted by other ships from a great distance. In other words; If they can see the ship they can also see if it contains the diamond. It will shine in the same manners as a “message in a bottle”/spyglass (but much brighter, so it's not difficult to distinguish those two), even when under deck, so there is no possibility to hide it on ones ship without other players able to see it. The only way to hide the diamond is by holding it (and the castaway pirate that clings to it) under water (it will float up to the surface if no one is physically holding it down in the water, and much faster than a tresure chest would do), or when the diamond is behind islands or waves (i.e. in a storm) or physical objects on an island, so there is a possibility to hide in these places while awaiting the heat to die down/ships to sail away.
The diamond will shine more frequently the closer one gets to the diamond, so one have a possibility to jump out in the sea (and hope the sharks leave one alone) immediately as one see a boat in the distance, thus preventing the enemy ship to see that you are carrying the diamond on your boat.
The Diamond is worth about 10000 gold, so it will be worth taking the risk to deliver it, or hunt for it.
When you are getting close to the island you’re supposed to deliver the diamond at (and the castaway pirate), there will spawn a pirate (friend of the castaway pirate) to receive the diamond and pay you the 10000 gold. This is to prevent other players accidentally or intentionally finding him before the diamond is delivered, and just be camping there until it does.
And that’s it! Hope I have explained this quest adequately and coherently enough, so people understands how it works. Please vote if you like the idea, and reply to bump the topic, and perhaps Rare will take notice then! Also, if you see any weaknesses with this idea, please let me know and preferably suggest a solution if you have any. As this idea is now, I think Rare easily could implement it in a weekly patch, and not with a “huge content update” (many months away), since the idea involves more or less already existing mechanichs (at least it appears that way to me, but I could be wrong, since I don't really know anything about programming games).
