I am about to run a short campaign/adventure for only one player and I've been working on the setting and story for a while now.
The Golden Thread of Aramoor
Setting : a small remote complex of islands, which lay far in the ocean, named Glealian Isles. The Isles themselves are a kind of a temple populated by monks and clerics, who have rejected their old lives and have dedicated themselves to serving the City of Aramoor. The Isles are self-contained, the monks and clerics (often called Glealians) grow and craft all the good they need, not much of communication exists between The Isles and the rest of the world.
In the middle of The Isles the City of Aramoor is located, which is not really a city, it is the main Glealian temple. A golden pillar of light ascends to the skies from the center of Aramoor. This pillar, called The Golden Thread of Aramoor is the bond between the Gods and the world. Glealians live to keep the Golden Thread tieing the two realms. Gods are merciful, never unfair and are very loyal to the Glealians. The Isles provide them with energy of magic rituals, which are being conducted by hundreds of Glealians during thousands and thousands of years, ensuring protection of the Gods over the world. The rituals have never been stopped and no negotiation has ever been attempted with the Gods, as the relationship is mutually beneficial and noone knows what would happen if the Golden Thread would cease to exist, so it continues to flow into the endless sky and in clear weather is visible from many mountains of the mainlands as a thin, yet powerful bond.
The Hook : a few months back the Thread has changed it's color, size and intensity of it's glow. Glealians have not responded to a single of the messages sent to them. The situation in the world is inexplainably heading towards chaos : cultist activity is high as ever, random attacks and assaults have been reported, though the attackers remain mysteriously unknown in every case. Volcanos are showing suspicios activity, domestic animals are running away and forming huge herds in the forests and during the nights the stars are flickering, as they are trying to stop emitting their light. Purple and grey flashes can be often seen in the skies, causing spontaneous panic outbreaks in the cities.
A scout expedition has been sent to the Isles, but has not yet returned, though it was scheduled to come back three weeks ago. The PC, a strong, but not so young battle mage/wizard/paladin/avenger (depends on his choice, but it should be something connected to magic and religion) has volunteered to travel to the Isles and investigate the situation. It sounds like a hopeless endeavour, but PC's ancestors were serving their duty at the Aramoor for centuries and he was the first to decline his faith of a monk and return to the mainland. So he, equipped, trained and full of hope, sails away in a small ship with 2 henchmen, who agreed to wait for him at the first Isle they can set their foot at. The PC believes in his ancestors and the Glealians and hopes to find an accident or a misunderstanding happening in Aramoor.
Aramoor : the City of Aramoor is a complex arrangement of floating platforms, bridges, ladders, lifts and spires of magic current. The whole structure has been built using calculations, which allow to amplify the energy of the rituals. It has many ritual areas, many small rooms for the serving monks to take quick rests, and a few utility areas to keep the ritualists supplied with minimal food, water and equipment.
The Real Story : the real cause of the failure of the Thread is an act of Cultist sabotage, which has been going on for decades, as it involved the infiltration of several generations in the serving monks of Aramoor. Their plan is to fail the energy supply, which will make the Gods not pleased, but still loyal and reasonably ready to negotiate. But then, the negotiations too (which are basically more of an "Excuse us, please" act) shall be sabotaged by the Cultists, which should make the Gods inevitably angry and dissappointed in the whole realm, leading to possible destruction or depopulation. Then the Cultists of the realm are planning to transport themselves to an another realm, ruled by the Cult, which will reward them for the destruction the caused, the the Cultist Gods shall now be able to devour and consume the realm, abandoned by the Gods. As of now, the Gods have sent down the Crows, an old dynasty of dark creatures who have been devoted to serving the Gods for thousands of centuries, as a sign of gratitude for saving them a long time ago. The Crows are used to test the strength and power of realms. They are black, almost featureless creatures, almost void of any personal will and not willing to betray the Gods.
Check out these pictures for approximate examples of their appearance :
Gameplay : the main portion of the game is going to happen in the City of Aramoor and will be centered around storytelling and combat on the platformic ares of the City. I would like to encourage the player to use ropes, acrobatics (though a bit limited in that, since his character isn't very young) and clever solutions to deal with the monsters. I don't want him to grind his way through the platforms, but I do want to give him a fair amount of combat encounters. Also I would like him to explore the Aramoor to find out more about the local magical features, items, constructions and interact with the environment. In terms of the atmosphere, I am leaning towards slowly building suspense, but with a huge amount of mystery, because the place is filled with magic and is basically, the magic vein of the realm. It should be something like the video game Journey, but a lot less abstract.
As of the character, I will allow him to make a Gestalt-type of a character (with multiple classes) and will encourage enchanting/crafting of his own items, as well as augmenting his old gear.
The Outcome : I usually like to see where the PC will be headed, what he will do and which decisions will he make, so then, between the sessions I will be able to come up with ideas for the ending of his quest. For all I know, he may reconstruct the ritualic areas and launch the Thread all by himself, he might ascend to the skies and have a word with the Gods themselves or sacrifice himself as a desperate act of trying to prove to the Gods that this realm has not turned against them (well, that would be mighty sad), I don't want to force anything on him.
I would like to hear feedback on my ideas, maybe some new ideas or corrections.