The dank, murky fog of an alien world ravaged by an unchecked viral outbreak is a prime setting for horror to unfold. The Callisto Protocol utilizes the Jupiter moon after which the game is named to great effect. Like its spiritual predecessor, Dead Space, The Callisto Protocol is a survival horror production coming from many of the same minds that crafted Isaac Clarke's horrific journey on the USG Ishimura.
While Jacob Lee's journey into the heart of terror is a narratively linear affair, that didn't stop the developers from inserting a few nooks and crannies in the blood-soaked pathways of Callisto for the more observant players. Trophy and achievement hunters are also most assuredly going to want to find every implant bio - most are along the main pathway, but a little bit of exploring can go a long way to obtaining all the accolades the game has to offer.
10 Elias's Cell
After the horror begins, Jacob is thrust into the violent chaos of monsters ripping through the cell blocks at Black Iron prison. In Chapter Two, Jacob makes his way around the facility and eventually returns to the cell block he initially left at the beginning of the chapter. Here, you can head down a large pathway lined with cells.
While making your way through the carnage, be sure to take Jacob up to one of the cells that are open. Inside, players will find a collectible bio for Elias, the character who partners with Jacob in his escape from the facility. Of course, this was Elias' cell.
9 Laundry Adjunct
In Chapter Three, players will find themselves amid the damp and steamy laundry room. This room is easily identifiable by the bags of laundry that are being carried along a railing on the right side of the area with clothes bins lining the floor.
When heading into this room, there are two paths to choose from. The mainline story path is in the door that is along the left side of the room. So, if you miss heading into the door on the right, you'll skip over a small area that takes you down near the actual laundry machines where the corpse of Officer Pruitt Matos lies with a bio implant waiting to be harvested.
8 The First Secret Room
In The Callisto Protocol, there are two rooms that are actually considered "secret" rooms containing journal collectibles that when collected and accessed will grant you The Commonality achievement. The first of these two areas is in Chapter Three shortly after the laundry room.
After heading down a mainline path that will lead into an underground bunker-like area, Jacob will jump through a hole in the floor down into another ruined hallway. Turning left down this path, you will notice a vault-like door that is cracked open. Squeeze through this crack to enter the first room and claim a journal collectible from the Warden, Duncan Cole.
7 Storage Hall
During Chapter Four, you will battle your way to Water Control. At one point, you will head down a hall with a big door on your right specifically for Water Control. Do not enter the room and proceed with your mainline objectives. Instead, continue on down the hallway past Water Control where you will find a door to the Storage Hall.
In this optional area, you can access an area containing plenty of loot in lockers. There's even a creepy shadowy sequence teasing the presence of more monsters, as expected. Proceed through the area to find a lab area where you can claim a journal recording from Dr. Jae Moon-Bell.
6 Botanical Harvesting
Jacob will eventually find himself inside an enclosed habitat on the surface of the moon. Here, one of the most tactical Biophage enemies known as the Rusher will assault you from the trees throughout the environment. So, stay frosty as these quadrupedal monstrosities are lurking in the shadows.
When entering the first area inside of Oxygen Processing there's an optional pathway in the door on the left side of the room. Don't miss it as it will lead you to a bio implant for Officer James Reese.
5 Tram Depot Entrance
Also, inside the habitat is the Utility facility which you will be able to access following your jaunt through Oxygen Processing. And, just like Oxygen Processing, there's an optional area that can be missed if it's not explored.
Upon entering the Utility building, there is a door on the left that will lead to a hall and area labeled as the Tram Depot Entrance. Ultimately, it's a dead end filled with various enemies. But the reward is a collectible journal recording for Officer Kyle Serra.
4 Remote Surface Building
Once Jacob is suited up to continue his mission of survival on the surface of Callisto, players will begin Chapter Five. After you first open a gate to an open area filled with derelict buildings, there is an open structure on the right labeled C2. Heading into this building will continue the mainline pathway.
However, collectors should skip this building initially and head to the back part of the area passed C2. Here, you'll find loot as well as another audio recording for Miranda Kristofich.
3 The Tank Inside The Control Room
While Elias' journey may have ended, Jacob soldiers on with Dani now the only semi-friendly partner he can rely on. In Chapter Five, Dani and Jacob will find their way back to the crash site of Jacob's ship. Shortly after, however, you will follow Dani along the moon's surface through a large double door that is cracked open.
After shimmying through this crack, you will find yourself in a massive garage. Following Dani will lead you along the mainline path. However, if you explore the backside of the armored tank-like vehicle on the right, you'll find that you can walk up inside the vehicle and collect the bio implant for Sgt. Scott Dvitny.
2 The Second Secret Room
This one is easy to miss as the pathway is camouflaged to a degree. In Chapter Six, you will find yourself climbing a ladder where the pathway to the Power Reactor resides immediately on your right. However, directly in front of you will be a partially destroyed wall that has a narrow crack in it. Believe it or not, you can fit through this crack.
This leads to a rocky pathway containing some blind enemies along the way. Eventually, you will come upon the secret room that contains the collectible audio recording for Yannick Sage. This combined with the previous secret room visit will unlock the aforementioned trophy or achievement.
1 Back Room In The Second Level Of The Colony
Once you find the colony that looks like a horrific shanty town of sorts, you'll climb a ladder taking you to a second level of the housing in the area. On the left, there will be a door that is optional to access that will take you to a back room.
Once inside the back room be sure to scan for any loot pick-ups. You will have to kill a blind enemy before you locate a bio implant for Derryn Barr.