Gryphon

Alien developed stars were sent to Babylon in 905 BC where, having fed on the minds of the people assumed the constellation that was named the Gryphon by the astrologer Urtaki. The Gryphon, made of light, became manifest and began an attack on the city before being trapped by the reflective power of mirrors. Cut off from its operator the Gryphon construct vanished several hours after capture, once the sun had risen, leaving behind an armful of silver disks that were safely collected up and taken away by the Doctor and Amy Pond in the TARDIS. (DWAM: In the Stars)