Eingyi is a deformed pyromancer who is dedicated to serving the "Fair Lady", Queelag's Sister.
Eingyi is a pyromancer from the Great Swamp but he was banished after creating poison based pyromancies. The Fair Lady sucked the blight pus out of him and many other residents, making herself sick in the process. This action so greatly affected Eingyi that he became her servant and carries her eggs to show his devotion. Although Eingyi is devoted to Quelaag's Sister, he cannot speak her language; everything he knows about her and her past is through observation and extrapolation.
Eingyi blocks the entrance to Quelaag's Sister. He will ask the player if they came to serve his master; the player must answer yes to access Quelaag's Sister, and thus, the Chaos Servant covenant without killing him. Eingyi is initially mistrustful of the player, however, if the player becomes infected and obtains the Egghead status, or speaks to Quelaag's Sister while wearing the Old Witch's Ring, he will see the player as a true servant and will open up extra dialogue.