The Pandorica Alliance was put together to stop the Doctor from destroying the Universe.
The Pandorica Alliance was a group of aliens who were trying to save the Universe from the Doctor. The cracks in time were the work of the Doctor. When the aliens teleported down to Stonehenge where the Pandorica was. The Doctor had fifty Roman Soldiers who were actually duplicates from Amy's book when she was a child. River Song founf this book and one about Pandora's box. The Pandorica was designed as a prison to keep the most deadliest creature inside it. That creature was the Doctor.
The Pandorica Alliance appeared in:
Series 5: The Pandorica Opens and The Big Bang