Throughout the Fortress Vimana level, there are doors blocked by a red light. This guide on How To Open Red Doors On The Fortress In Indivisible explains what you need to do in order to complete the requirements of the red doors and progress further into the fortress.
Like many obstacles in Indivisible, such as tree roots, the red doors require you to complete a specific objective before they open. However, this is not like the axe or other items, as the red doors are only featured on the fortress level. As such, it’s a singular, unique objective that you must complete, as opposed to getting an item to use on future doors.
How To Open Red Doors On The Fortress In IndivisibleThere is a small room near the very end of the fortress level. It’s part of the story, you cannot miss it. Inside the room is a small computer like device. When Ajna attempts to smash the device, a boss will spawn. Once the boss has been defeated, Anja proceeds to smash the device.
This allows you to use the elevator, which is directly tied to story progression, and it also lifts all the red security barriers blocking the other doors. And that’s How To Open Red Doors On The Fortress In Indivisible.