Fafhrd and the Gray Mouser return in Sword of Sorcery 2 (April/May 1973) for another adaptation of a Frtiz Lieber tale by O'Neil and Chaykin.
This story is a lot of backstabbing fun, and is based on a tale called "Thieves House," which seems appropriate. At the top of the story Fafhrd and the Gray Mouser are hired to steal a jewelled skull, but the man who they do this for drugs them and takes off.
While they try to pursue the guy to get their pay they face all manner of other thieves, all plotting against each other, trying to get possession of the skull. As well, Fafhrd gets approached by some ghostly spirits, the ones who the skull truly belongs to, who intend to get it back.
I'm making a guess but there is a feathered woman, Iulis, who Mouser tricks at one point, tying her up, though she returns at the end of the story. I get the feeling that she might have been a recurring character in the Lieber stories, simply by the kind of easy relationship she has with the two men.
At the end the ghosts come for the skull and kill the evilest of the thieves, who is also the most cunning, and therefore in possession of the skull after outdoing the other baddies.