The Water Mill Gear Chest is one of the 9 Assassin’s Creed Mirage Gear Chests collectibles in the Wilderness area, and it allows you to unlock another Hidden One Dagger / Upgrade Schematic for Basim. To unlock the AC Mirage Water Mill Gear Chest, however, you’ll need to find a key that requires Basim to swim a bit.
The Water Mill Gear Chest Key in Assassin’s Creed Mirage is underwater in one of the mill’s aqueducts. Even though the Gear Chest also involves a small puzzle, obtaining the key to open it is the trickiest part.
AC Mirage Water Mill Chest Location
Before going after the Water Mill Chest Key, let’s see where to find the actual chest you need to open. As you can see on the following map, this AC Mirage Gear Chest is found north of the Water Mill Viewpoint in the Wilderness area—specifically, southeast of the Dur-Kurigalzu Gear Chest and east of Caravanserai.
After synchronizing the Water Mill Viewpoint, perform a Leap of Faith to return to the ground, then move north across the river. While standing in front of the giant wheel that powers the mill, head left but remain on the street level. Eventually, you’ll see an ally leading to a house and a movable shelf.
The first thing you’ll want to do here is approach the shelf and pick up the anvil blocking it. You should see it on the ground. Pick the anvil and throw it away, then interact with the shelf and move it to the right. Now, get inside the room behind the shelf to see three chests. The Gear Chest, however, requires a key.
Where To Find the Water Mill Gear Chest Key
The Water Mill Gear Chest Key in Assassin’s Creed Mirage is found southeast of the chest you need to open, but it is underwater. From the chest you have found, head back to the giant wheel and follow the narrow alley behind it. When you reach the other side, head left, and you’ll see a small wooden fence. Behind it, on the walls, you can also see two smaller wheels.
Jump over the fence and scan the area under the first wheel on the left side (pictured above). Remember that the Wilderness Water Mill Chest Key in Assassin’s Creed Mirage is underwater, so you’ll have to dive to get it.
After you collect the Watermill Chest Key, head back to the small room where you have found the Gear Chest and open it to collect the Hidden One Dagger / Upgrade Schematic for Basim.