These items are crucial for progression, unlocking new areas, and advancing the story. Card Keys are particularly important, as they gate access to most of Outer Heaven's facilities.
- Card Key 1-8: These numbered keys are used to open corresponding numbered doors. You'll find them sequentially throughout the game. Always try to open doors with the highest numbered key you possess.
- Transceiver: Acquired from Gray Fox, this allows you to contact Miller, Diane, and Jennifer for additional support and intel.
- Oxygen Tank: Allows Snake to survive underwater for a limited time, necessary for navigating submerged passages.
- Uniform: A disguise that allows Snake to walk past certain guards undetected for a short period. Its effectiveness is limited.
- Compass: Helps you navigate in certain confusing areas, pointing you towards your objective.
Missing a key item, especially a Card Key, can halt your progress. If you find yourself unable to open a door, backtrack and search thoroughly for the required key. Prisoners often provide hints about their locations.