Any of the Shackled City story hours (including my own) should have players visiting the Abyss at some point (the layer of Occipitus is featured several times, and a fallen Demon Prince is fairly central to the story).
My Travels through the Wild West SH ended with a trip to Zelatar, and a confrontation with the Demon Prince Graz'zt. My Shackled City Epic protagonists are currently engaged in a rematch with him.