Key of Osanalan
From Halopedia, the Halo wiki
Template:Ratings Template:New Content The Key of Osanalan is a Forerunner object underneath the city of Cleveland, Ohio on Earth.[1] As revealed by a captured Colonel James Ackerson, without the Key, the Halos will not properly activate. Outside of Halo: Uprising, no mention of the key is seen in Halo 3, and Master Chief activates the replacement Installation 04 successfully even without the key. However, it appears the key does not exist at all. During their childhood, Colonel Ackerson and his brother, Ruwan, made up an object called the Key of Osanalan for their make-believe games.[2] It is likely Ackerson told the Covenant about the key to prevent them from simply destroying Cleveland, and his brother.
