Sorry, haven't been on the boards in a while.
The Campaign in a nutshell:
The PC's are regular nightlife hustlers. A gambler, A Drugdealer, The Drugdealers Muscle, A Con Artist, And a Docter who lost his license to practice due to a drug abuse problem.
The PC's went to an underground Casino run by mafia for an illegal boxing match. The Con Artist used to be a boxer, so the group had to go. Anyways the Jamaicans we're there and they didn't like one of the PC's friends Alex (for a scuffle at the club earlier), and Alex was the drugdealers major sellers at a local nightclub. So one of the Jamaicans decided to sell one of Alex's friends a pill that pretty much made the guy spray his internal organs out of his mouth. (strange pill eh?)
The Jamaicans dipped, and the entire night was ruined, and the PCs were the only ones left standing. Lou Giovanni, Mafia Head of all of NYC and NJ was pissed about the fact that a hit was performed in his establishment and told the PCs they have 1 week to find the Jamaican who did this or else he will hold the PC's personally responsible.
So they go to a bar where the Jamaicans usually hang out and find that its completely empty. They go inside and a strange (tiefling) bartender told the PCs that Abdula (The Jamaican) was gone. The PC's threaten the bartender, so the bartender tries to calm them down with free drinks.
Of course a successfull sense motive check reveals that the Bartender has no reason to harm the PCs in anyway, he was just doing his job (whatever that is...) so they each take one of his drinks. He then tells them to walk through a steel door.
They walk through the steal door, and in my Campaign the Plane of Shadow Borders our world. The Bartender co-exists in the Plane of Shadow and enlists the help of Aya, a Human NPC who was trapped a loooong time ago and now works for the Bartender to guide the PCs to the only place that can take the PCs where they want to go. The River Styx.
Now The backstory is that Abdula was always dabbling with the occult, it started with Voodoo and eventually led to a downward spiral. Abdula talked with a nameless spirit years ago (how Abdula contacted this spirit is unknown to the PCs). This spirit offered Abdula knowledge, and in turn Abdula would tell the Spirit about his world.
Soon a gatekeeper was sent to Abdula, and a Door to other worlds was open to the back of his bar. It took alot of effort since Earth's pattern works with Science, so its hard to get something like this done, but it gets done. Abdula had to adhere to Planar Laws.
Unfortunate for him he didn't, and he brought *something* back with him that he shouldn't have during one of his journeys to the outer planes. Something that killed the PCs friend.
For all the PCs know they think the bartender just dropped lethal doses of LSD and they are just hallucinating. Either way they are on a mission.
In short, the Planes are a completely different cosmology with different laws and physics (duh!). Earth was shut off from the planes looong long ago and was never re-visited until now. Since Earth has gone in the ways of Science it is now a completely different pattern at work, so a trade route hasn't really been established. The PCs will learn few of the Many Planar laws from a defect "Inevitable" they will soon meet. And one of the Laws is that upon establishing a doorway to a new Plane/World representatives from Mechanus are suppose to meet with the leaders of that Plane/World. Therefore some other unknown entity is at work.
And with the bloodwars going on again, who knows who contacted Abdula.
BTW Dreamscapes run alllll through the cosmology. Plane's/World's like Earth have dreamscapes too, but Humans aren't mentally capable (unless aided with other forms of stimuli) to navigate them or interact with them correctly, so most dreams end up being lucid, or vivid, and easily forgotten. Of course if Earth becomes part of the Grand Cosmology again, they can start working magic again.
The PC's will have a HUGE problem to deal with. I think I got most of the Plot covered, if there is any other questions just ask. I'm leaving alot of it out. I got about 40+ pages of notes for the campaign world alone here.