Putrified Ducts is an optional area in Silksong located in the top right corner of the map, offering valuable tools beneficial for exploring Bilewater's swamps. There are two routes to reach it: through Bilewater or Memorium. The Bilewater route requires defeating the boss Groal and is challenging without the Wreath of Purity, which neutralizes maggots in Bilewater. The Memorium route is recommended and requires the Clawline and Faydown Cloak, allowing access to hidden paths. In Putrified Ducts, players can find the Wreath of Purity, the Apostate Key, and a haven for Silksong fleas. The final Pale Oil needed to upgrade Hornet's needle can be collected from Fleatopia in Act 3.