Im thinking of running a new PS game...But its going to be a little over the top and difficult i think to piece together...so here goes...
Running a group of say 5 pcs...there all amnesiac and wake up together at lvl 1. Now I want my players to write a background (extensive!) on there characters. However Im thinking of having one of my pcs the BBEG even though he might not know it.
My adventure would start them in Sigil, due to none of my pcs have played or know PS or PS:T so I think it'll make a good location for the learning curve. The gist of my adventure is this...over the coarse of the adventure they will start getting little memories back that they can puzzle back together and start pieceing there lives back together.
Im going to have them trek to Mechanus and Acheron and maybe one of the inner planes.
The mechanus trek I was going to include a Moigno but with a difference. My underdstanding is that Moignos get more visible the older and more mathematically complicated they get so I was thinking maybe a 900 year old or 1000 year old (I think the eldest is max 1000). But this moigno has met a kindred spirit in an old Mathematician and someone fused together with him/her (i dont know, im thinking), so when the pcs meet him/her (im still not sure) but he will talk in mathematical symbols and have numbers and symbols run across him eyes and as he blinks they change direction. Also was thinking as he moves he sort of walks and shimmers as numbers and equations fall off him.
The Acheron part I want them to get through the plane so some various encounters as they make there way down to Ocanthus. The simple thing would be to have their memories wiped by the styx and they hear tales of how the styx is frozen at the bottom and may contain their memories (opens with a Knock spell, apparently 
). Though I was thinking on this to and might have them have to steal/buy some empty sensate stones and as they open the ice crystal that contains the memories the memories are sucked into the sensate stones to store them.
I dont know at the moment its still in planning and will need alot of it...but i have 3 weeks so I think I will get it there...any ideas or additions would be appreciated.
OneOfOne - barely a DM but getting there!
Just a side note really, once they've got their memories back, how about one of them remembers they have a item in their pocket that opens a portal to Sigil.
A easy way to end it, just because you have your memories doesn't mean the Lower Planes are going to be a place you want to fight back out of!