Deep Dish Dungeon Key: Small, Iron and Prison Key Chain

The chain, in the order it happens

Every step below gates the next one, and skipping ahead usually means walking back. The in-game door text tells you which key it wants: "Door Locked. Bring the …" followed by the name.

The first Small Key is generous: the door it unlocks leads toward the prison, and the game says so with a sign rather than a puzzle. The Hammer is the first real detour, because the sewers are where the handwheels, the water and the crouch holes live.

The Big Smelter is not the smelter you build

This trips up almost everyone. The Smelter in your crafting menu is a station you build with 5 Clay and 5 Scrap Metal. The Big Smelter already stands in the dungeon, casts items from molds, and needs no clay at all.

To cast an Iron Key you need 5 Coal, 8 Scrap Metal and the Iron Key mold in place. Its mold set also covers three Key Pieces and a plain Key, and the door that wants those three pieces is the Jaguar Door in the Barracks.

The error strings tell you what is missing, if you read them: "Smelter is cold. Add more Coal." · "Smelter is empty. Add more Scrap Metal." · "Add casting mold before activating." If you see no message at all, check your build — patch 1.0.50.0 fixed a prison mechanism that failed to show its "Bring Chains to Fix it" prompt.

Small Keys are a different currency

Small Keys are not the Iron Key chain. They open the plain locked doors scattered through the dungeon, and the counts are lopsided enough to plan around.

Chests holding Small Keys turn up in the Prison (two of them), the Castle (one) and the Small Cave (one). Inside the prison, two of the cell chests contain Small Keys, so the region partly pays for itself.

Where the Prison Key sits

The Prison Key comes from a small chest in the same stretch of the dungeon as the Big Smelter and the Jaguar Door, close to one of the Key Piece molds. The same chest holds a Club, which is how most players remember the room.

That placement matters before you go looking: the key is not inside the prison, so searching the cells will never produce it. You need the Iron Key door open first, and that means a cast Iron Key.

The Jaguar Door and the second key

The Iron Key door stands in a hall that leads to the Jaguar Door, and getting into that hall takes a second key. Carry the mold from the room beside the smelter onto the second lock and cast again, then open the door with the large keyhole near the smelter.

The same furnace also casts the three Key Pieces that open the Jaguar Door itself. Its mold set covers three pieces plus a Key and an Iron Key, so a single visit can serve both doors if you bring enough coal and scrap.

The Jaguar Door is a treasure door rather than a progress door: the Silver Dagger sits behind it. If your only goal is the prison, you can leave it shut and come back when your stock allows.

The demo is different in a way worth knowing. There the smelter wants 10 Scrap Metal instead of 8 and one Key Piece mold is disabled, so the Jaguar Door never opens at all — not a bug, and not a puzzle you are failing.

What to bring before the prison door

The prison is where the dungeon stops being gentle: skeleton archers shoot from cells, cobwebs block doorways, and at least one mechanism wants repairing before it will move.

• A lit torch, held in the right hand, for cobwebs.
• The Hammer for the rusty bars between you and the cells.
• Two Small Keys, minimum, for the cell doors.
• At least one iron rod, kept back for the lever.
• A bow or a shield, because the archers shoot first.
• Food that raises stamina, since the walk back to camp is long.

The pickaxe is inside the prison rather than before it, so do not plan a route that assumes you already have one.

The coin route that runs alongside all this

Two stone coins — Sun and Moon — sit in the kitchens on either side of the bat dining hall. Put both in the hands of the water-spouting statue and the water level drops, revealing a chest in the Marble Ruins that holds the Gold Talisman.

That Talisman is one of the six gold treasures for the Inner Castle chest, so this side route is not optional if you intend to finish the true ending. Leave both coins in the statue; taking one back raises the water again.

Quick answers

Where is the prison key?

In a small chest behind the Iron Key door, in the same chest as a Club. You cannot reach it before smelting an Iron Key.

How much does the Iron Key cost?

5 Coal and 8 Scrap Metal at the Big Smelter, plus the mold. The demo build wanted 10 Scrap Metal instead of 8.

Where do I get the hammer?

In the sewers, beside the rusty bars it opens. It is a pickup, not a craft, at that point in the game.

How many Small Keys do I need?

More than feels reasonable: the Temple alone has eight Small Key doors, and the Prison has five. Collect every one you pass.