Marathon Guide: How to Crack the Upper Complex in Dire Marsh
Leaving an extraction zone with empty pockets is miserable, but this secret boss gauntlet guarantees you walk away heavy.
Marathon's Dire Marsh at night is an absolute nightmare on a good run. Surviving the hazard zones and hostile squads is an achievement by itself. If you want to extract with gear that actually justifies the stress, you need to locate the Upper Complex. This hidden area locks some of the best Purple and Gold loot in the game behind a multi-room gauntlet and a nasty boss fight. You can pull this off in both Standard and Sponsored Survival modes.
I'm going to show you exactly how to find the required access codes and clear the facility without getting sent straight back to orbit.
Hunting the Observation Labs Keycard
Before you start dreaming about a full inventory, you need the Observation Labs keycard. You can't buy or craft this item (which is honestly a shame). It's a random drop, and farming it requires some serious legwork.
I highly recommend bringing the Triage Shell for this run. The healing bots will keep you on your feet while you run around burning your currency. You need to locate Network Towers around the map's various points of interest and pay 3 UESC CERTs to activate them. This triggers a drop sequence for Supply, Weapons, and Gear Caches.
Each Cache contains three separate chests, and the keycard can randomly spawn inside any of them. Just hit whichever Cache is closest to you and hope the RNG drops in your favor. Make sure you rip open a Weapon Cache while you're looting, because you're going to need a massive stockpile of ammo for the upcoming fight. You can technically get the keycard by hunting down random Warden spawns, but picking fights with elite enemies just for a chance at a drop is a fantastic way to end your run early.
Breaking Into the Upper Complex
Now that you hold the keycard, you need to actually breach the facility. You have two options here, and your choice dictates whether you walk in quietly or start a massive firefight.
Surviving the Button Gauntlet
Getting inside only solves your first problem. The Upper Complex is a sequential puzzle spread across three separate rooms, and it drains your resources fast.
In the first room, you have to activate the upstairs terminal. This lights up three green buttons scattered around the immediate area. Shoot all of them to open the door directly below the terminal. You repeat this exact process in the second room with four green buttons, and then again in the third room with five green buttons.
Before you waste a full magazine spraying randomly at the walls, you should absolutely equip a weapon with Darksight Optics. Looking through that specific scope reveals hidden numbers next to every green button. If you shoot them in ascending numerical order, the game rewards you with an extra loot room after the boss fight.
There's also a secondary puzzle involving seven red buttons hidden across the entire complex. Unless you have a massive amount of time left on your extraction timer, completely ignore the red buttons. Hunting them down takes way too long and almost guarantees you'll miss your ride out.
Defeating the Gold Shield Warden
You finally made it to the back room. You'll find one last terminal where you insert the Observation Labs keycard to kick off the main event.
Activating the terminal immediately spawns a hostile wave. You have to fight them off while shooting another set of green buttons to progress the encounter. You must survive three full waves of this chaos before the game finally drops the gold shield Warden on you. This boss hits incredibly hard, so use your cover and manage your distance. Once you put the Warden in the dirt, a final security door opens to reveal a room packed with Purple and Gold loot. Grab your gear and get to an exfil before a rival squad catches you reloading.
