ACV Siege of Paris Hidden Ones Bureau: Where to find Diodurum Ruins key, Gisacum Ruins key, Champlieu Key

It's been an action-packed week for Assassin's Creed Valhalla as the Siege of Paris expansion is now live. It's the second expansion so far for ACV with loads of new content now up and running on the Ubisoft servers.

Near the mid-point in the story arch for ACV, you'll reach an area West of the Paris slums and you will come across ruins from Roman times. Within these ruins, you will find an underground entrance for the Hidden Ones Bureau.

Inspect the dead guard in the bureau entrance to find out Bellatores Dei soldiers have been searching for keys to unlock the door. These keys can be found in the Diodurum Ruins, Gisacum Ruins, and Champlieu Ruins.

Diodurum Ruins Key

On your map you'll find the Diodurum Ruins, they're close to the Hidden Ones Bureau, so head there first. Within the ruins, there is a wooden trap-door covering an underground entrance.

Destroy the wooden covering, but don't jump down below. Head into the water below the synchronization point and swim through the doorway arch.

Through the doorway arch in the water, you'll come across a hidden room. In the hidden room, you'll find a closed door with the Assassin's logo on it.

Open that door and follow the pathway inside until you reach the dead end. Use the red explosive jars to throw and destroy the wall and reveal the final room.

Inside this room, you'll find the Diodurum Key, as well as the Book of Knowledge which will grant you the Golden Flame ability.

• Read more: ACV The Siege of Paris: Release date, price, gameplay, enemies, armour, and weapons

Gisacum Ruins Key

There are about six or seven soldiers total in the Gisacum Ruins, so it's quick work to take them all out. This will make completing the rest of this quest a lot easier.

Look around in the corners of the ruins for another wooden trap door. Destroy it, and this time, hop in. Be aware, there are large swarms of rats upon entry, so slash at them with your flame until they retreat and run away.

You'll see another door with the Assassin's logo on it, open it and your rewards will be inside. Along with the Gisacum Ruins key, you'll find a Wealth Chest.

Use the red explosive jars again to destroy the stone walls in front of you and find the Book of Knowledge. You will gain the Plague of Rats ability, allowing Eivor to coat an arrow with rat bait, attracting a swarm of rats to attack the arrow’s landing point.

Champlieu Ruins Key

The last key can be found in the Champlieu Ruins, through a wooden trap door underground. Destroy it and drop down and slide through the small holes in the corridor to pick up a red explosive jar.

Blow up the wall with the jar and find the room containing the Champlieu Ruins key. Before leaving, go further down the corridor and slide the movable cargo out of the way to the other side of the room.

Moving the cargo will reveal a dropdown hole into another secret room. This last room contains the Book of Knowledge which will grant you the Goule Breath ability.

The ability allows you to fire an arrow causing a target to vomit involuntarily. Nearby hostiles who see this will back away in terror.

• Read more: AC Valhalla: Siege of Paris expansion, Discovery Tour, Year 2 content, and more

Return to Hidden Ones Bureau

Once you've gathered all three keys, head back to the Hidden Ones Bureau. There will be a piece of Opal on your left when you enter, grab this and use it to find the Hidden Ones logo on the floor, which you will then follow.

Use a red explosive jar to blow up the stone wall and enter the final room. In this room, (along with swarms of snakes) you'll find a Wealth Chest containing the Joyeuse short sword (legendary weapon).

After this, you can leave the Hidden Ones Bureau. You'll notice that the logo beneath you is lit aflame on your way out, a pretty cool touch from Ubisoft.

You'll also find a mysterious letter on your way out where someone named "AC" says they will "stay unknown in the darkness, so that you may work in the light." Perhaps this AC will come back into play further down the road.