Before I start, I just want to thank everyone who reads and responds to my post.
I'm a new GM that is getting ready to start to run a Adventure Path. Hopefully, if all goes well, I'll end up running multiple AP's.
Before I started I wanted to share my Grand vision and get feedback of my "enhancements".
These are the enhancements I want to implement:
All APs level the characters up to level 20.
All APs are tied together somehow that tells an even bigger story.
A reoccurring non-critical character that keeps popping up over and over.
Also, each AP needs still needs to be able to stand on it's own.
So here is my grand idea.
Start by running Curse of the Crimson Throne. Sometime during the adventure a stranger has the players retrieve one of the pieces of the Shattered Star. (This would add enough content to allow the players to level to 20) I'm thinking the stranger would be the Whispering Tyrant
The second module I would run would be Rise of the Rune Lords. Once again, the stranger asks this group to get a different piece of the Shattered Star.
This pattern would continue through the modules
Return of the Rune Lords
and Hell's Vengeance
Finally, the last module would start out with the stranger asking the adventures getting the final piece of the shattered star. Once he completes the pieces then finish the story line up with Tyrant's Grasp.
This idea would make the Whispering Tyrant my main evil baddie that has been manipulating the events all along in his rise to power. Logically this would have to cause shattered star to run backwards, since this would allow me to delay having to adjust encounters for several months until I get my feet wet.
Any advice, suggestions, and possible problems I would encounter would be very much appreciated.
Most of the plot issue caused by these modifications should be fairly straightforward to maneuver around. There is one that could prove a problem, though:
the Whispering Tyrant is sealed away in Gallowspire and cannot leave its confines until the halfway mark of that AP.
Beyond that, let me just give you a general piece of GM'ing advice that will serve you well: players are unpredictable and will seldom do what you expect them to do. Especially with all the abilities at the disposal of high-level adventurers, there's every possibility they may investigate or confront your mysterious stranger at a much earlier junction than you'd prefer. Part of GM'ing is adapting when things don't go to plan, and with a mega-campaign spanning 5 AP's you'll definitely need to rethink your plans along the way. Remember that each AP will have your players add their own mark to the world; this is material for you to use.
It's a fascinating concept, but that is one gigantic cookie, and the bite you're planning is enormous.
I don't know what your organization and improvisation skills are like, but it's one heck of a lot more than I'd recommend to the typical starting GM. I might do something like that, but I have 40+ years of experience behind me, and I know my weaknesses.
Still, it could work. I'm not trying to nay-say, just give fair warning.
So if I understand correctly, you are planning on running multiple APs, with different characters (although presumably the same players) that all go to level 20 and that each contain bits of foreshadowing and plot elements that will all connect to a final AP.
That could be really cool, but I imagine it will be pretty hard to accomplish. Depending on how often you play, completing a single AP can take years to finish. Even if your group has a pretty heavy gaming schedule, I see this as being a minimum of several years to complete this. If your gaming group isn't stable over this period, a lot of the cool factor will be lost, since any new players would miss all the foreshadowing. It also seems a little weird that the players would see foreshadowing, but the characters wouldn't since (presumably) they change between the paths, so their character's won't know anything about the mysterious stranger the other party encountered.
This doesn't mean you shouldn't go for it if the idea excites you, but those are some things I would think about. The biggest thing is making sure that each AP is good and fun on its own.
I'm a GM who just has a year+ experience running Kingmaker. I deviated from the plot a bit in book 1, and basically threw book 2 away.
My strongest advice to you is: Read through ALL of the APs and materials you plan on using, especially since you're going to try and tie in multiple APs. I threw Kingmaker book 2 away because it felt so much like book 1 I said, "I wouldn't want to play this if I were a player, so why would I want to GM this?" CoCT has lagged at many times for me, but that might have been my GM. Since you're going to embellish and tie in different plots together, make sure you create the overarching connections well in advance, because when your players go where you weren't expecting them, as Dasrak said, you might have to recreate the plot threads you were about to weave. GMing has been a lot of work but fun for me. Good luck to you!