The Worn Keycard is one of those items that sits in your inventory without any obvious purpose. It's a 5★ Mission Item in Arknights: Endfield that unlocks a single abandoned storage room in Aburrey Quarry, and the game gives you almost no guidance on where to use it. If you bought it early and forgot about it, or stumbled onto the locked door first and couldn't figure out how to open it, here's exactly what you need to know.
Quick answer: Buy the Worn Keycard from Lonnard in the Staff Lounge of Aburrey Quarry for 100 Stock Bills, then use it at the locked gate on level B1 of the Listening Post to access an Aurylene and some gatherable materials.
Where to buy the Worn Keycard
The Worn Keycard isn't a random drop or quest reward. You purchase it from an NPC merchant named Lonnard, who runs a small shop inside the Staff Lounge building in Aburrey Quarry. The item costs 100 Stock Bills and appears under the Grocery category in his shop menu.
Getting to the Staff Lounge requires powering up a deactivated Electric Nexus that blocks the entrance. You'll need to transmit power from a PAC using Relay Towers and Electric Pylons. When approaching the Staff Lounge area, you'll notice you're on a higher floor with a lift nearby. Place a Relay Tower or Electric Pylon near the lift, start transmission, ride down to the ground floor, and plug the transmission cable into the Electric Nexus. Pull the lever to unlock the gate, which triggers a brief conversation with a nearby NPC. After that, you're inside the Staff Lounge.
Head south through the building and look for Lonnard in a corner to the east. Open his shop, switch to the Grocery tab, and purchase the Worn Keycard. Once bought, it permanently sits in your Mission Items inventory and doesn't get consumed when used.
Locating the locked door in the Listening Post
The Worn Keycard opens a gate in the Listening Post section of Aburrey Quarry, specifically on the lower B1 floor. This door is tucked behind a puzzle sequence that many players complete without noticing the side path leading to the keycard gate.
Step 1: Progress through Aburrey Quarry until you reach the Listening Post area. This happens naturally as you clear the quarry's main content and side missions like "Fix the Super Crane."
Step 2: Inside the Listening Post, find the combat puzzle with numbered electrical generators and energy gates. You need to attack the generators in a specific order to drop the barriers. The code is 4–2–3–1, which is also written on a nearby wall once you're inside the puzzle area.
Step 3: After opening the energy gates and moving through them, turn left instead of continuing forward. You'll find an elevator lift tucked into this side path.
Step 4: Take the elevator down to level B1 and follow the path to the bottom. At the end of this route, you'll reach the locked gate that accepts the Worn Keycard. Interact with the machine nearby to open the storage room.
What's inside the storage room
The rewards behind the Worn Keycard door are modest but relevant for exploration completion. The main prize is one Aurylene, which counts toward Aburrey Quarry's total Aurylene collection. If you're tracking down every instance of this collectible for stamina upgrades, this one is required.
The room also contains some gatherable materials scattered around the environment. Destroy the box to the side to get additional resources. Climb the crates and jump down through a hidden opening to reach more materials on a desk. The tunnel entrance leading to the Aurylene is behind some fallen shelves, which can be easy to miss if you're not looking carefully.
There are no additional missions, cutscenes, or unique gear tied to this keycard. Once you've collected the Aurylene and swept the room for materials, the Worn Keycard has served its purpose.
Why this item is easy to miss
The Worn Keycard sits at the intersection of several systems in Aburrey Quarry: power routing to access the Staff Lounge, the internal staff areas where Lonnard sells it, and the deeper Listening Post levels where the door is located. You're asked to revisit the quarry multiple times for main and side missions, which makes it easy to see the locked door early, forget where it was, and only later pick up the keycard from Lonnard.
The item also doesn't show up as a standard quest marker with a dedicated mission. Unless you keep notes or drop map pins, you can easily end up with a key and no clear memory of the corresponding gate, or vice versa. The generator puzzle code (4–2–3–1) is worth remembering since you'll need to solve it to reach the elevator leading down to the keycard door.
The Worn Keycard is a straightforward cleanup task once you know both locations. Buy it from Lonnard in the Staff Lounge, ride the elevator down past the generator puzzle in the Listening Post, and claim the Aurylene waiting behind the gate. It's not a major reward, but completionists will want to grab it before moving on from Aburrey Quarry.
