This is a flexible, long-term campaign designed to take a party of characters at first level, and watch them die horribly. That's not to say there will be any foul play involved - it's just that manifesting new dragonmarks in the middle of Sharn is not a good survival strategy.
Along the way they will meet full parties of PC-level adventurers aiming to kill or subdue them; escape from an island prison; make extremely powerful enemies (and possibly even friends); lose everything and fight desperately to get it back; discover parts of the Prophecy related to the dragonmarks and, just perhaps, form their own dragonmarked house, carving out a place in the hostile political environment of Eberron.
Maybe they will even discover the secret of their own marks, and save the world from the very edge of destruction...The War of the Mark left no doubt as to the victors. The thirteen ruling Houses are considered by many to be more powerful than the nations they span. This power comes not only from their innate advantages in various key areas of life, but from their ruthless protection of their near-monopolistic empires. Other marks have come and gone, but none have been allowed to survive. Even those manifesting recognised dragonmarks live more or less under the constant mercy of their associated houses.
None of this, of course, has ever been of particular relevance to you. You were not born to a dragonmarked house, and had no particular connection to those who were. Until, perhaps, the nightmares began.
They started as simple visions of dragonmarks. Not too surprising in itself, although they did seem extremely realistic considering that you'd never seen them before. The details became clearer and clearer, and always linked with an unclear but desperate purpose. Soon you were remembering the shape of the dragonmark in the daytime, and eventually you went to research it.
The thing about the particular dragonmark that haunts your dreams and fills your mind's eye, is that it doesn't exist. You can't find any reference to it anywhere, and the reaction when you drew it once for a librarian was creepy enough to cause you to laugh it off as a flight of fancy. Later, you burned the paper.
Then came the itching, and finally, the pain. A particular patch of your skin started with a little tickle. Days later it was a lot of a tickle. A day after that, you were non-functional with pain. Somehow wary of going to a House Jurasco hospice, you stagger to a temple dedicated to Olladra and offer a donation in return for some care. It is there that you find that you are not alone...