1. Get into the forge basement
- First collect the Hammer from the sewers.
- Return to the large hall and take the basement stairs on the right of the large doors.
- Break the rusty metal barrier with the Hammer.
- Search the basement rooms for Coal, Scrap Metal, the oversized keyhole and casting molds.
- Continue to the Big Smelter at the end of the forge route. This machine is already built; you do not need to craft a separate camp Smelter.
2. Cast the key for the side room
- Find the mold that is already fitted to the Big Smelter. Keep it in place.
- Add 5 Coal to the lower fuel supply.
- Add 8 Scrap Metal to the upper crucible.
- Operate the lever to cast the key. Loading the materials without pulling the lever will not complete it.
- Pick up the finished key. Save it for the right-hand room beside the Jaguar Door; that is where you obtain the Prison Key.
3. Cast the larger key for the basement lock
- Return to the nearby forge rooms and find the larger mold beside the oversized basement route.
- Carry the mold to the Big Smelter. It is a heavy object you hold in the world, not a normal inventory item; set it down if stamina runs low.
- Swap in that mold, then add another 5 Coal and 8 Scrap Metal.
- Pull the lever and collect the new key.
- Take this key to the oversized keyhole near the basement entrance and open the door to the Jaguar Door corridor.
For both early keys together: 10 Coal + 16 Scrap Metal. The three Jaguar Key Pieces use additional casts.
4. Use the correct key at each door
| Door or puzzle | What to use |
|---|---|
| Oversized lock in the basement | Key made with the large mold |
| Side room right of Jaguar Door | Key from the mold fitted to the Big Smelter initially (often called Iron Key) |
| Inner barred door beyond the prison's webbed stairs | Prison Key found in the side-room chest |
| Jaguar Door with three sockets | 3 Key Pieces, not either of these two keys |
5. If the Big Smelter is not producing a key
- Confirm the mold is mounted rather than left on the floor.
- Check that the lower fuel supply has Coal and the upper container has Scrap Metal.
- Pull the lever after both supplies have been filled.
- Read the finished item's label and return to its intended lock. If one key does not work, do not use extra materials repeating the same mold—check whether you need the other mold instead.