If you’re exploring Hollow Knight: Silksong and want to unlock the Cogwork Heart, you will need to track down three hidden Cogheart Pieces. Each one is tucked away behind a bell puzzle, and once you have all three, they will merge into the Cogwork Heart automatically. This item is key to progressing the story since it powers up the Second Sentinel. In this guide, we will walk you through where to find each Cogheart Piece, how to solve the puzzles, and what to do with the Cogwork Heart once you’ve got it.
How To Get All 3 Coghearts
In Hollow Knight: Silksong, Cogheart Pieces are important key items. You will need to collect three of them to automatically combine them into a Cogwork Heart. This special item is used to activate the Second Sentinel, which plays a role in progressing the story. You will find one Cogheart Piece in each of the following locations. All of them are hidden inside bell puzzle rooms, and you will need to hit the bells in the correct order to unlock each piece.
Choral Chambers – Bell Puzzle Room
For the first Cogheart Piece, head towards the Choral Chambers. Before you head toward the Slab, climb up to the room above. Clear out the enemies in the vertical shaft, and you will see the fragment sitting near the top ledge. Using a double jump makes this part easier, but careful wall hopping will also get you there safely.
Solve two bell sequences in order:
- First sequence: 3, 6, 5, 1, 7
- Second sequence: 2, 4, 6, 3, 5, 1
Completing both will reward you with 1 Cogheart Piece.
Whispering Vaults – Bell Puzzle Room
The second Cogheart Piece is hidden in the Whispering Vaults. Make your way through the chamber until you reach the upper platforms. In a small hidden alcove, you will find the fragment. You will need Cling Grip to safely climb the walls and reach it.
This one has three bell sequences you need to solve:
- First sequence: 1, 2, 7, 4
- Second sequence: 7, 5, 6, 4, 5
- Third sequence: 2, 7, 3, 5, 6, 1
Finish all three correctly to get 1 Cogheart Piece.
Memorium – Bell Puzzle Room
The final Cogheart Piece is tucked away in the Memorium, a secret area to the right of the elevator in the Cogwork Core. You will need precise platforming and the Clawline ability to cross the gaps and reach it. Once inside, defeat the waves of Pilgrim enemies, and then you can claim the piece.
Like the others, you will find a bell puzzle here. Solve it to collect the final Cogheart Piece.
- First sequence: 6, 5, 4, 3
- Second sequence: 4, 5, 2, 4, 1
- Third sequence: 2, 7, 3, 5, 1
Where to Use the Cogwork Heart
Once you’ve collected all 3 pieces, they will automatically combine into a Cogwork Heart. To use it:
- Head to the Cogwork Core, located on the western side of the map (just left of the Bench).
- Look for a large inactive automaton.
- Insert the Cogwork Heart into it.
- Doing this will awaken the Second Sentinel, who will start fighting enemies in the area.
Cogheart Pieces are unmissable if you’re exploring thoroughly, but the bell puzzles can be tricky; make sure to hit the bells in the exact order. No extra tools are required to collect the pieces, just good timing and memory. Activating the Second Sentinel may affect enemy behaviour in nearby areas, so be prepared.
