Osgood Box
From Tardis Wiki, the free Doctor Who reference
The Osgood Box was a device given to Osgood and her Zygon duplicate by the Doctor to use if the ceasefire between humans and Zygons broke down after a peace treaty was arranged. (TV: The Day of the Doctor) The two Osgoods recorded a video explaining the Osgood Box before one of them was murdered by Missy. (TV: The Zygon Invasion, Death in Heaven)
