In Deus Ex, The Conspiracy isn't the only thing that can trip players up:
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- Midway through the game, when you finally meet Tracer Tong in Wan Chai Market, he tells JC Denton (the player) that one Dr. Feng (a Versalife employee who worked on the augmentations JC and Paul Denton have) went missing in the Canal Road Tunnel. The actual tunnel (that is, the one accessed from a passageway right beside Tong's compound) is not where you need to go. Instead, the player must go to the Old China Hand bar (which is in another part of the map), access an unassuming vent in the bar's freezer area (which is difficult to get into because of problematic controls) and follow a long passage and ladder down to a flooded section filled with Karkians. However, doing so gets you another aug upgrade canister and rifle ammo, along with an Apocalyptic Log written by Feng.
- Several of the alternate and optional conversations in the game require the player to do things in Violation of Common Sense, such as waiting to talk to characters until the last possible moment in a level or backtracking long distances to hear different dialogue. JC has a completely different conversation with the captured scientist in the New West Coast Silo if you hold off on talking to him until after you've killed Howard Strong and are ready to exit the level (which means backtracking through pitch-black tunnels), while several of the citizens in Paris have different conversations about the police presence if you wait to talk with them until after you've met Nicolette Duclare, had the conversation with her at the helicopter outside La Porte L'Enfer, and refused to leave. The alternate solution for the situation onboard Lebedev's jet requires you to kill Anna Navarre, at a point in the game where the player still believes the character has Story-Driven Invulnerability.
Deus Ex: Invisible War
- In Deus Ex: Invisible War, the special weapons. Most are in out of the way areas you wouldn't otherwise think about, including a sewer, the bedroom of an apartment dweller, under some junk in an antique store, and a utility hallway. The worst though, is the Hellfire Boltcaster, which is hidden in a small room only accessible by jumping over to a small ledge in an area you don't have much inclination to be in anyway (it frigging off one faction to the point of sending assassins if you complete the objective there.)
Deus Ex: Mankind Divided
- A prominent example in Deus Ex: Mankind Divided is Marchenko's killswitch. You have two opportunities to get this item (which helps during the final boss battle if you're going the lethal route), but both of them are so well-hidden that you will not find them unless you have OCD-like tendencies of thoroughly examining every item and room you come across. The first is hidden in the G.A.R.M. facility — and in a first for this game (and likely the series), the only way to access it is to crouch-jump on top of a set of lockers, look down and press a hidden button wedged between the lockers and wall, which opens a compartment in one of the lockers that has a switch. The second is found in the final level itself — in a box hidden under a table. Up to this point, the game has never given an indication that there were items hidden in boxes, and the player is never led to believe otherwise. The second killswitch doesn't even show up on Smart Vision due to being inside another object, either.
- Getting the "best" outcome for the Dvali Enemy Civil War. Getting Otar and the rest of the Dvali operatives to remain civil when you visit the old Prague Theater in the third act not only requires you to have done all of the optional objectives that Otar gave you earlier in the game, but also knock out or kill Radich Nikoladze during the second visit to Prague, despite nothing in the story telling you to do so besides a couple of vague emails talking about Radich and Otar's relationship. Not only that, but completing the objectives in the opportune fashion requires you to use lethal methods (and thus break a non-lethal run). If you choose to let Louis Gallois escape (via faking his death and assuming a new identity) instead of killing him and his bodyguards outright, Otar and the rest of the soldiers will still be hostile when you arrive at the theater. This is despite him telling you earlier on that you've completed his favor if you do all the requisite tasks.
- The "Golden Rookery" achievement requires you to carry an oversized gold-plated pigeon from Ivan Berk's apartment right near the start location in Golem City to a hidden area within ARC Territory. Aside from the fact that Berk's apartment isn't even immediately noticeable from the ground (you have to climb several floors to get to it — the map doesn't help matters), the final destination requires that you've invested in the "Punch Through Walls" aug. And that's not even getting started on the bugs that can cause the penguin to disappear if you stray too far from it, especially within the Throat.
- In the "System Link" DLC, getting all the Praxis Kits (which are in short supply in the mission) requires the player to visit ShadowChild's secret room before you know she exists in the first place, at a point in the mission where Adam has never heard of her and no one else has mentioned her.