While the undead are the main enemies you will focus on in Modern Warfare 3 Zombies, there are plenty of still-living threats as well. Scattered around the map are mercenaries who can lay the hurt on you if you are unprepared. These enemies can be found in different spots, but in no other location are they more dangerous than in fortresses. To get access to these buildings, you need a particular key. Here is how to get a Fortress Keycard in Modern Warfare 3 Zombies.
Where to get a Fortress Key in MW3 Zombies
To get a Fortress Keycard in Modern Warfare 3 Zombies, you first need to get into a Stronghold. Before you can do that, you need a Mercenary Stronghold Keycard. Those can be obtained by taking out a Mercenary Convoy or purchasing it from a Buy Station for 2,000 points.
Once you have the Stronghold Keycard, find a Mercenary Stronghold on your map. These locations can be in the same spots as Infested Strongholds, but have a different icon on the map. If you go to an infested one, it will not give you the opportunity to get the Fortress Keycard.
Before jumping into a Mercenary Stronghold, be sure you have a reliable weapon and plenty of armor. Given that these buildings have tight corridors, you can make all the enemies inside funnel into vantage points that you can take advantage of. Slowly work your way through the building, defeating anyone that gets in your way. While looting the area, look out for a big safe that you can drill into. Similar to the Raid a Weapon Locker contract, you will need to stand by and defend this safe as enemies attack that area while it drills. When it is opened, interact with the safe to find the Mercenary Fortress Keycard along with some other good items.
Now that you have a Mercenary Fortress Keycard, you will need to go to Legacy’s Fortress, located in the northwestern portion of the tier 2 zone. Unlike Strongholds, this Fortress is always in the same spot.
Before you go, make sure you have good armor, and we highly recommend at least a weapon that has been pack-a-punched twice. Also, do not try to do this solo. You will want to be in a squad of at least three people, but preferably more. Try to find other players that want to join you. Fight your way through all of the enemies and traps and you will faceoff against Legacy in the upstairs of the Fortress. Defeat this hulking enemy to get a bunch of good loot in the next room.