Hidden Ones’ Robes – Jorvik
First, locate the graveyard in Jorvik’s far southeast corner, and then the breakable floor you can descend into. It’s just a case of following the tunnels and sticking to the right until you come to the main room of the bureau. You can then climb a nearby bookshelf to retrieve the key and open the chest.
Hidden Ones’ Hood – Colcestre, Camulodunum Bureau
By far and away the trickiest bit of gear to find, this one requires you to first locate the felled free right on the southern outskirts of the city. It’s inside the city walls, but it’s more or less leaning on them from inside. Take an explosive jar from the nearby shop and use it to smash the breakable floor after you’ve climbed the tree and over the wall.
Now drop down and continue through the tunnels. You should spot an opening above you and to the the right. It’s about halfway down the tunnel. Climb up and keep going until you reach the flooded room.
Swim to the end and dive down, following the underwater passage and then the path after that. You’ll eventually appear at the end of the flooded wall but just above the locked door and where you first dived down. Jump across to the other side and down into the next area.
Now dive into the water pool and retrieve the key, then hop out, unlock the door, and then walk into the room to peer through the metal fencing. See the barred door? Shoot it out, then return from the direction you came, back to the other ledge and down the stairs to open the now unbarred door. that will unlock the door nearby. The chest is there.