Gaslighting

It's time to find the anti-immortality artifact Black Mark in Dark Valley and put an end to Shadow of the Monolith once and for all.
Warning: After a certain point in this quest, the Monolith truce gained after Beard's backpack will end and all Monolithians will once again become your enemies.
== Walkthrough ==
=== Cave ===
Before leaving the Cave, Miner hands us a Positioner that will let us track the GPS coordinates of the stash containing the artifact.
=== Dark Valley ===
The stash is located in Dark Valley, directly underneath the bridge over the irradiated swamp. Coincidentally, it's right underneath the radioactive symbol on the minimap.
Pick up the artifact and quickly stash it in a single artifact container if you aren't wearing the Prophet's Star. Head to Labyrinth - you can get there quickly from Undiscovered Land.
=== Labyrinth ===
You can freely clear out all of the natural Monolith spawns on the map without softlocking the quest. Shadow and his squad are scripted not to attack yet even if their reputation shows them as enemies. Enter the bunker and climb up the ladder to see Shadow flanked by his four machinegunner goons.
Strelok offers Shadow a "rare artifact," fooling him into picking up the Black Mark and unknowingly nullifying his own immortality. When pressed about Living Water, Shadow will refuse to offer any information and the Monolith truce will be broken for good. Shadow and all four machinegunners will begin firing on you during a white screen flash.
The conversation between you and Shadow is not translated, at least not at patch 15.03.23
==== Surviving the meatgrinder ====
If any one of his squad dies before you speak to him, the rest will become aggressive, disqualifying Gas canisters as a good setup option here. The safest way to survive this encounter is pre-placing Plastic explosives all around them and running down the ladder during the white screen flash, safely detonating from the floor below. Popping one Morphine will also give you enough time to Rambo everyone in the room with a good weapon.
Pick up the Shadow of the Monolith note and the Black Mark from Shadow's body. The secret to his immortality is the Living Water artifact, which is "hidden in itself and covered with a radiation background."
=== Cave ===
Return to Miner to let him know the news. Apparently, this was not Shadow himself that was killed, but his identical brother. Miner advises you to hold onto the Black Mark so that one day Shadow can be destroyed.
Right after you end the conversation with Miner you are messaged by Sakharov to meet with him.
This completes the Black Mark section of Chess Player, and leads directly into the Living Water quests which can be continued after playing Chessplayer's Dictaphone No10.
The conversation between you and Miner is not translated, at least not at patch 15.03.23
== Notes ==
== Bugs ==