In Doctor Who’s 2010 story “The Pandorica Opens,” the Pandorica is a prison.
The Pandorica is introduced as a legendary object supposedly containing the most feared being in the universe. When it opens, however, the Doctor discovers that it is designed as an inescapable prison for him. The story uses the name as a science-fiction echo of Pandora’s box: an apparently mysterious container whose opening changes the situation dramatically.
“The Pandorica Opens” is the first part of a two-part Series 5 finale written by Steven Moffat. It was followed by “The Big Bang,” and the storyline centers on Amy Pond, Rory Williams, River Song, and the Eleventh Doctor.
The Pandorica is therefore not simply a box or a weapon. Its defining function in the episode is containment: it is a prison constructed to hold the Doctor.