Assassin's Creed Hidden Ones' mission: Where to find the keys and the Joyeuse short sword

During Assassin's Creed: The Siege of Paris, you'll have the opportunity to discover a new Hidden Ones' bureau and uncover more secrets about the mysterious group. You'll also be able to get your hands on a new short sword, Joyeuse, which become poisonous after successive heavy hits. 

You'll most likely stumble across the Lutetia Bureau accidentally and will discover that you'll need three keys to open the door, so here's where to find them and how to get the Assassin's Creed Valhalla short sword.

Where to find the Hidden Ones' keys 

To pick up this quest you'll need to reach Sigfred's forward camp and search for a letter on the table from Pierre. This will start the Hidden quest, where you'll need to find three keys in different ruins. The three ruins you're looking for are: 

• The Champlieu Ruins
• The Gisacum Ruins
• The Diodurum Ruins

Finding these ruins is easy as they show up as waypoints on your world map. Most of the ruins have guards nearby so you can choose to sneak your way around or deal with them all first. The keys are all found underground and in the Diodurum and Champlieu ruins: you're looking for floorboards to smash through to reach an underground entrance.

Each key can be found behind a Hidden Ones' door that Eivor can open. Head inside, loot whatever you find, and pick up the key. Watch out for rats, though, as they can zap your health in record time. Once you've got all three keys, it's off to the Lutetia Bureau.

How to find the Lutetia Hidden Ones' Bureau and get the Assassin's Creed Valhalla short sword 

The Lutetia Bureau is pretty easy to find. It's in Paris, just northwest of the Paris fast travel point and west of the Boatmen Baths Tavern. Again, a waypoint will show on the map, so don't worry if you haven't visited it before. There aren't any guards to fight, which is good news.

Once inside, you'll see a Hidden Ones' symbol on the floor below and a blocked doorway. Make your way around to the left, jumping over the ledges and batting away rats to reach an oil jug. Carry it back with you and throw it at the blockage, clearing the door.

Inside are a bunch of snakes, so deal with them and open the gold chest. You'll receive the Joyeuse short sword for your efforts. On the way out you'll find a mysterious letter that shows a few Hidden Ones remain in Francia, though they do not wish to be found. It's signed "AC", so make of that what you will.