In the Back 4 Blood Campaign, there are 10 Secrets (aka Golden Skulls) for players to collect in order to complete 10 different achievements/trophies.
The 10 Secrets are hidden as golden skulls in various levels waiting for players to pick them up. At the moment, however, they only can be found while playing online co-op rather than in the Solo Campaign mode, which is something Turtle Rock Studios is reportedly working to fix.
For those achievement hunters out there, here's a breakdown on where to find all the Secrets (Golden Skulls) in Back 4 Blood.
Back 4 Blood Secret Locations Guide: Where to Find the 10 Golden Skulls
The golden skulls can be collected simply by walking up to them, in which the game will then prompt you to press something and pick it up.
None of them are missable, meaning you can replay the mission they are in at any time and collect the ones you don't have.
Lastly, the game will automatically save the Secrets shortly after you pick them up, so you don’t have to play to the end of the mission after finding them, but it’s likely best to wait until the related achievement/trophy pops up on-screen before doing so. Once collected, the Secrets cannot be picked up again.
Secret No. 1: Port Man Toe?
In "The Crossing" in Act 1, after crossing the bridge and nearing the ferry for the first time, the golden skull can be found by taking the closest stairs down one level, hugging the right wall and in the front right corner of a reddish metal container inside a briefcase.
Secret No. 2: Bell Hop
In "Book Worms" in Act 1, when you’re scouring the area for more survivors, you’ll come across the Haven Apartments building where you have to blow up the basement door with the gas canisters to get in. Head inside and go up to the first floor. Directly across from the stairs you took to get to the first floor will be a connected office room. Underneath the desk with a laptop and a notepad on it will be the second golden skull.
Secret No. 3: Pallet Cleanser
In "Special Delivery" in Act 1, just outside of the mission-ending safe house, there will be a lumber yard. Climb on top of the dumpster by the red metal container outside the lumber yard and jump across the pallets until you reach the third golden skull.
Secret No. 4: Easily Mist
In "Hell's Bells" in Act 1, in the marshy, foggy forest before reaching the tool shed, climb the large rocky mound between the trailer with turtle plushies and the small wooden shack to find the fourth golden skill hiding in some shrubbery by the highest tree.
Secret No. 5: Cooped Up
In "A Call to Arms" in Act 2, after getting out of the parking structure, go to the rightmost part of the area. Ignore the makeshift bridge, drop to the street below to the right, make a left around the corner and keep going until you see a chicken coop by a garden and a wooden fence. Behind the metal fence of the chicken coop, you can find the fifth golden skull.
Secret No. 6: Dangerous To Go Alone
In "Hinterland" in Act 2, when you get to the underpass with the big arch bridge, turn around to the waterfall you just dropped from to find the sixth golden skull in the water.
Secret No. 7: Cryptozoologist
In "Grave Danger" in Act 2, outside of the mission-opening safe house, head to the cemetery on the right and look for an open crypt in the back right. Just inside to the left will be the seventh golden skull and a turtle plushy.
Secret No. 8: Night of the Living Hedge
In "Garden Party" in Act 3, after completing the maze to get to the mission-ending safehouse, go forward towards the other part of the maze rather than taking the stairs. Make a quick left to find the eighth golden skull sitting on top of a stone cup.
Secret No. 9: Extra Credit
In "Making the Grade" in Act 4, after exiting the gym and climbing up to the roof, head towards the mission-ending safe house but hug the right side. Before the metal stairs, turn right behind the large metal boxes to find the ninth skull in a blue and yellow tent.
Secret No. 10: Mind Your Step
In "The Abomination" Act 4, when you get the objective to "destroy the body weakspots," walk across the narrow veiny bridge and go up the immediate right branch to find the 10th golden skull wedged into the wall.