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There are two connected secret levels located on the east side of the map in Hollow Knight: Silksong, and both areas are brutally difficult. This is your classic Poison Swamp area — places like Rot Lake in Elden Ring are a good example. They’re full of traps, have annoying status effects, and they’re generally unpleasant to explore. There are two of these areas in Silksong and they’re both surprisingly difficult to find. Here we’re going to explain how to find each entrance. They’re both huge areas with a lot to explore — you’ll especially want to delve into Bilewater ASAP.
How To Enter Bilewater | Secret Level

To access Bilewater, Hornet needs the wall-jump ability and access to Sinner’s Road.
- This secret level is accessed through Sinner’s Road. Outside the Styx NPC, there’s a vertical chamber. On the right side of the shaft, there’s a hidden breakable wall that can only be reached with wall-jump or double-jump. Reach it and break through to find the secret Bilewater level.
Bilewater is a disgusting, fetid swamp filled with traps and dark passages. Bilewater has two major directions — both lead to a secret boss fight. If you travel south, you’ll encounter The Mist, a special maze with no clear way to progress. It leads to a boss fight against the Phantom — defeating her unlocks a parrying mechanic.
It also has one of the longest, toughest platforming areas in the game — it leads up to an optional entrance to the Putrefied Ducts, the second secret area in this guide. We’ll talk about how to enter that area of the map below.
How To Enter Putrefied Ducts | Secret Level

To access the Putrefied Ducts, reach the Memoriam at the top of the Citadel. West of Songclave, the long corridor, there’s a spot in the ceiling you can only reach with a double-jump. It leads up to the Memoriam section of the map. You’ll need the double-jump ability and access to the Citadel’s Choral Chambers in Act 2 to enter the Putrefied Ducts.
- From the Memoriam, reach the lower east corner to find a map room. Jump into the hidden passage on the ceiling of the map room to find a path that leads to the exterior of the citadel.

- Go right across the bridge until you reach a rock wall on the east side. On this side, climb up to find a hidden breakable wall. Smash it to find the hidden entrance to the Putrefied Ducts.
Alternatively, you can travel through Bilewater. Learn how to access Bilewater in the guide above.
- In Bilewater, you’ll need to traverse to the top of the area. This is a huge area with a very difficult platforming path to the top and no benches.
- There’s an enemy encounter and tough boss fight found at the border right before entering the lower level of the Putrefied Ducts. This path is essentially required for sequence breaking and is extremely difficult. Unless you’re very skilled at the game, you’ll want to use the Memoriam path.
At the bottom of the Putrefied Ducts, you’ll find an NPC called the Huntress. Her hut is located in the maggot-filled water on the lowest level of the area. She gives the Broodfeast Hunt and naturally these are more difficult than your average hunts. Everything in these strange areas is worth exploring, and there are more mysteries to solve in these two secret levels.
