If you’re wondering how to uncover the mystery of The Callisto Protocol Kallipolis and unlock ‘The Commonality’ achievement, you’re not alone. You can easily reach the end of Jacob’s pulse-pounding excursion through Black Iron without even realising you’ve missed it, and even achievement hunters may be stumped by the incredibly vague achievement description: ‘uncover the mystery of Kallipolis’.
Thankfully, we’ve scoured every inch of one of the best horror games of 2022 and located the secret rooms of Black Iron prison, where the shady dealings of the Kallipolis are laid bare in incriminating audio logs. These secret rooms are also filled with useful supplies, including items that you can sell for The Callisto Protocol best upgrades – though you’ll need to know where to find The Callisto Protocol weapons to make use of them. All that being said, here’s how to locate the secret rooms to discover The Callisto Protocol Kallipolis mystery and unlock ‘The Commonality’ achievement.
Callisto Protocol Kallipolis room #1 location
The first secret room is located in the ‘Outbreak’ chapter, immediately after receiving the ‘Locate the Medical Facility’ objective. Instead of taking the door to the right to progress, head left towards Supply B426. The door to Supply B426 is locked, but there’s a blood-smeared vent to the right you can squeeze through. Drop down into the rubble and follow the linear corridor until you reach a half-open door. The gap is pretty small, but you can shimmy through it to reach the first Callisto Protocol secret room.
As unnerving as this secret room may be, there are no enemies lurking to catch you unawares. A cache to your immediate right contains a pristine energy convertor, health injector, and hand cannon ammo. Be sure to pick up the ‘Secret Room 1’ audio log located on the desk at the end of the room.
Callisto Protocol Kallipolis room #2 location
The second Callisto Protocol secret room can be found during the ‘Below’ chapter while completing the ‘Locate the Power Reactor’ objective. Advance through the Power Station until you reach the ladder that takes you up to the Power Reactor control room. Instead of turning right at the top of the ladder, turn your attention to the crevice immediately in front of you.
Pass through the crevice to enter a cave system crowded with tentacles, corpses, and egg sacs. The path here is linear, so follow it along and drop down to the lower levels of the cave. There are several Blind enemies fused to the walls down here, so be sure to remain crouching and take them out with a silent backstab if they begin to stir, or use the GRP to remove them from the wall before you reach them.
There’s a crossroads at the end of the path, with a flight of stairs to your right and a passage to your left. Continue along to the left – be careful, there’s a Blind that’s ready to unstick itself to the wall – and find a gap between the cave wall and the gate to your immediate right in order to gain entry to the second secret room. The Callisto Protocol ‘The Commonality’ achievement unlocks automatically the moment you step inside.
The second secret room is arranged exactly like the first, though this one has a Bloodworm in the middle of the room that’ll immediately grab you as you advance forward; take it out with a quick gunshot, or get ready to mash that action button. Once it’s dealt with, you’re free to snap up the health on the table to your left, and the ‘Secret Room 2’ audio log at the end of the room. There’s also a cache containing a CPU printer, skunk gun ammo, and a health injector. Once you’re finished in the second secret room, head back into the cave and take the stairs up to the Power Reactor control room.
That’s all the direction you need to uncover the mystery of The Callisto Protocol Kallipolis and unlock ‘The Commonality’ achievement. Now that’s done and dusted, take a look at our guide to defeating The Callisto Protocol two-head boss if you’re tired of being ripped apart by one of the most punishing biophage mutations Black Iron can throw at you. If you’ve reached The Callisto Protocol ending, you might be curious about when we can expect The Callisto Protocol new game plus – it’s sooner than you might think.