The Constable armor set is a brand new, spiffy-looking outfit that you can obtain in Bloodborne: The Old Hunters. You might recognize it as the outfit worn by Valtr, master of the League, the new covenant dropped with the latest Bloodborne patch. However, you’ll need The Old Hunters expansion itself if you want to obtain the full armor set.
To get the Trousers, go to the Hunter’s Nightmare lamp and exit from the door to the right. If you haven’t unlocked this shortcut, you’ll have to make your way to the river of blood and onto the bridge where there are several foes waiting for you. Just below the bridge, you’ll see 4 of the blood-spewing spider ladies standing in the corner with their backs turned to you. They’re guarding the Constable Trousers. Take note that you can’t backstab them as they’ll kick you with their hind legs. Try luring them away one by one for a more manageable fight. After taking them down, go to the spot they were standing at to pick up the Constable Trousers.
From the river of blood, continue making your way up. You’ll soon come to a blood-soaked area full of dogs and a hunter-type enemy. Once you’ve dispatched of them, make your way up the ladder. If you look down to the area from where you came, you’ll see two wooden beams beneath you connecting the structure you’re standing on to another platform. Jump down to one of those beams and make your way across to get the Constable Garb.
If you’ve already unlocked the Nightmare Church lamp, you can start from there and run past the 2 giant Cthulhu-like monsters, and up the ladder at the end. This will allow you to bypass the dogs and hunters, and go straight to the wooden beams.
Master’s Iron Helm
To get the final piece of the Constable set, you simply need to crush 5 vermin and talk to Valtr. To get vermin, you have to use the Small Resonant Bell to join another player’s world and help them defeat bosses. You’ll get 1 vermin for each boss you help to defeat. After you’ve collected 5 of them, go to your inventory and use them all. Head to the Forbidden Woods lamp, and talk to Valtr inside the small shack.
After you’ve spoken to him, leave and reset the area. Go back to the shack and you’ll find that he’s left his helmet on the ground.