I1 (Dwellers in the Forbidden City) was an absolute classic; playing it was like reading Jewels of Gwahlur by REH.
I’ve ran it both in 1E and 3E games, played it in 1E and also adapted it for a d20 Cthulhu game.
I used Against the Cult of the Reptile God, who was a capturing slaves for the Dwellers of the Forbidden City, on the Isle of Dread. (They were searching for the Forgotten Temple of Tharizdun, but the party never got there.)
Best campaign I ever ran.