During the Rot in the Slums quest, to ingratiate themselves with their new ally Sigfred and deal a powerful blow to Charles the Fat's hegemony in Francia, Evior has one objective: Assassinate Engelwin, the crooked Bishop of southern Paris.

As always, you have the option to fight your way into his fortified church the dumb way. But the Assassin's Creed Valhalla's Siege of Paris DLC see the return of "Black Box" missions, where the lethal assassin can find multiple ways towards carrying out their hit.

Here's how you unlock Bishop Engelwin's Assassination Event.

Assassin's Creed Valhalla Siege of Paris | How to unlock the Engelwin Assassination Event

Your first port of call is the nearby tavern, where you need to speak to the innkeeper about potential leads.

At the tavern, you're pointed in the direction of a pining drunk and a church scribe who may have learned too much about Engelwin's dealings.

You only need to complete one of these to set you on the path towards the Assassination Event, and both are as easy or difficult as each other.

Drunk Path

Speak to the drunk, and he'll ask you to save his daughter from some Parisian guards.

Follow the quest marker to where they're holding her, then defeat the paltry gang however you wish.

Meet up with the daughter nearby, and she'll say that she sold the key to the church gate to some bandits.

Descend into the sewer entrance next to her to search for the key.

Follow the linear path, defeating the bandits along the way, until you reach a storage area. After dealing with the two guards, take the key to the northern gate of the church from the table.

Scribe Path

To follow your lead with the Scribe, head to the quest marker on your map and speak to the nun in the plague district.

She'll give you a new marker which takes you into the sewers over your left shoulder.

Swim down the tunnel, climbing over obstacles and diving under the water when necessary. Then at the end, you’ll find the scribe.

They have the watchword - Job 1:21 - which you can say to the guard at the front gate of the church to gain access.

Triggering the Assassination Event

Now head to the church and enter through your desired route. Whichever method you choose to get inside, the next steps are the same, so don't sweat too much over which you pick.

To start off on the route towards the flashy Assassination event, climb the northern side of the church.

Sneak inside the open door, then speak to the man on the mezzanine level.

He says he's next up to be judged, but is having cold feet. Offer to take his place, and the man will tell you you need a special robe to enter the basement.

You can steal the Bellatores Robe from the chest next to the man on the mezzanine level which, when equipped, gives Eivor unfettered access to the basement of the church.

Don the Bellatores robe, go down the ladder next to you and descend the stairs on the other side of the church.

Speak to the Priest at the bottom of the passageway, then walk inside.

Light the braziers on either side of the altar when the nun gives you the riddle, then continue down the stairs of the now-open room.

You'll emerge in a large chamber where Engelwin performs his rituals.

To get to him undetected, sneak down the middle of the room, avoiding the guards by not going down the stairs to your right.

Your only objective is to interact with the glowing light you see with your Odin's Vision in the middle of the water without raising the alarm.

Speak to Engelwin, then disrobe when instructed, before taking the timed opportunity to assassinate when it appears.

Leave the chamber the way you came in, then unlock the door across the next room. Shift the shelves on the left-hand side of the Bishop’s office, then interact with the two journals on either side of the cubby.

Now read the journal in the corner of the main office, before interacting with the scythe behind the desk. This gives you a new objective in your quest to find Charles the Fat.

For more how to spend your time in Francia, here's where to find all three Frankish Nobles.

Or if it's loot you're after, here's how to complete the Roman Excavations for the Hidden quest.