Probably my favourite adventure either. I ran a 9 year Planescape campaign involving a bunch of custom modules, interspersed with some of the stand alones (Harbinger House, Well of Worlds, ran them through the Great Modron March, and finally through Dead Gods.
Fantastic, with some really creepy places like Tcian Sumere and the lost planet of Moil. I think we still have to finish the last part of the adventure, when the PCs go to the Astral......the campaign ended with the characters capturing the Rod of Orcus, and realizing they would be hunted to the ends of existence. To keep it out of his hands, they ended up getting themselves hipped on the Prime. One of the characters, a dwarven monk, offered to sacrifice himself, but the party didn't want to abandon him, so they all escorted the Rod through a malfunctioning one-way portal to the Rainward Isles of Taladas, where they became trapped in the Age of Mortals, with malfunctioning magic, and portals back to the planes that were unreliable or inaccessible. The intent was to throw the Rod into the burning sea of Hitehkel, with the intent of destroying it.
That was when the campaign ended, with the characters feeling they might never be able to return.
The intent was that after running another game for a while, we'd revisit the campaign, with the action of getting to the Burning Sea, possibly dealing with a Dragon Lord, and eventually, years afterwards, being able to return to the planes, to deal with Tenebrous' corpse on the Astral.
Unfortunately, the group dissolved, so I don't think it will ever be resolved.
Banshee