When your team is dropped into the Complex, you enter the Rundown. It’s a sequence of expeditions issued by the Warden, the unknown entity holding you captive.
The Warden has issued a new work order
A new work order from the Warden means a new Rundown. Survive all the expeditions to complete your mission and clear the Rundown. Of course, the further down you go into this abandoned research facility, the tougher things get. But that won't stop you because while you don't know what the Warden is up to, your program doesn’t allow for questions. New Rundowns will drop periodically, bringing your team grisly new ways to suffer.
Up until Rundown 7.0, every new Rundown would overwrite the previous one. However, something in the Complex has changed, causing all past nightmares to resurface permanently.