Genshin Impact: How to Find and Use the Key of Ancient Design (Locked Door Quest)

The Locked Door quest in the House of Hesperides hinges on one item, the Key of Ancient Design, which sits hidden inside a row of ice Matryoshka dolls in the Mountain Mansion Front Hall. Grab the key, open a nearby door, and you free a Jack Frost that was sealed away by another Jack Frost standing guard.

Quick answer: On the House of Hesperides Main Floor, use the Prime Ice Construct menu to dismantle the ice Matryoshka doll, pick up the doll under the shell three more times to reveal the Key of Ancient Design, then turn around and use it on the door southwest of the room.

What you need before starting

Access to the Mountain Mansion is gated behind a single item, the Invitation to the “Ritual”. You earn it by working through the Hesperides of Love and Hate World quest, which unlocks the interior where both the key and the locked door are found.

Everything for the Locked Door quest happens on the House of Hesperides Main Floor, also called the Mountain Mansion Front Hall. Head there first, then look for a table holding a row of Matryoshka dolls.

The Key Of Ancient Design Location In Genshin Impact-1 — The Mountain Mansion Front Hall on the House of Hesperides Main Floor.

Get the Key of Ancient Design from the Matryoshka dolls

The key is not lying loose on the table. It is buried inside an ice Matryoshka doll, and you peel it apart layer by layer using the Prime Ice Construct ability.

Open the Prime Ice Construct building menu while standing near the row of Matryoshka dolls on the table.

Aim at the ice Matryoshka doll and dismantle it. Breaking the icy shell exposes a smaller doll underneath.

Where To Find The Key Of Ancient Design In Genshin Impact-1 — The highlighted ornament shows the doll you interact with to keep digging.

Pick up the doll that sits under the icy exterior. Repeat this three more times, working through each nested layer.

Collect the Key of Ancient Design from the final layer. The moment you take it, the nearby Jack Frost starts acting worried, which is the clue that something is sealed behind the door.

Open the locked door and finish the quest

With the key in hand, you do not need to travel anywhere. The door is right behind you.

From the spot where you collected the key, turn around and face the door on the southwest side of the room.

Interact with the door and confirm the prompt to use the Key of Ancient Design. This frees a Jack Frost that the guarding Jack Frost had locked away.

Where To Use The Key Of Ancient Design In Genshin Impact-1 — Confirm the prompt to spend the Key of Ancient Design on the door.

Follow the freed Jack Frost and watch it smack the Jack Frost that trapped it. Once that plays out, the Locked Door quest completes and an Exquisite chest appears for you to open.

Exquisit Chest Location In Genshin Impact-1 — The Exquisite chest that appears once the two Jack Frosts settle their dispute.

Rewards and Intricately Patterned Buttons

The Exquisite chest can hold Intricately Patterned Buttons. These are a trade currency, not a cosmetic on their own, and you spend them at the Jack Frost Goodie Shop in Jack Frost Village.

Note: The shop stays closed until you finish the Small Jack Frost, Big Trouble World quest. Until then, hold onto the buttons.

Exchange item	What it does
Weapon Appearance	Cosmetic skin for a weapon
Prime Ice Construct Appearance	Cosmetic skin for the Ice Structure
Level-up materials	Character or gear progression items

You know the quest is done when the Locked Door objective clears and the Exquisite chest becomes lootable after the two Jack Frosts finish their scuffle. If the door will not open, the most common reason is that you have not yet peeled all four doll layers to actually pull the Key of Ancient Design.