Key items are crucial for progression and unlocking new areas. Card Keys (Lv. 1-7) are found after defeating bosses or completing objectives and are used to open locked doors. The PAL Key is central to disarming Metal Gear REX. The Disguise (found in the Nuclear Warhead Storage Building) allows you to temporarily blend in with enemy soldiers. The Gas Mask protects you from poisonous gas. Always be on the lookout for these items, as they are essential for advancing the story. Some key items are automatically acquired, while others require careful searching.
