The Festival of Offerings was a millennial ceremony on Akhaten. It was a system-wide event, with all those who had a belief in the beginnings of life being with Akhaten gathering to watch.
During the ceremony, the Queen of Years would sing the Long Song to feed the Old God, or "Grandfather," and keep him asleep. Then the Queen would be sacrificed to him, either willingly, or by the Vigil if she resisted.
The First Doctor visited with his granddaughter. At a time when the Eleventh Doctor and Clara Oswald visited the festival, they also saw, among other species, some Pan-Babylonians, a Lugalirakush, some Eukanians, a Hooloovoo, a Terraberserker from the Kodonian Belt, an Ultramanta and Dor'een. (TV: The Rings of Akhaten)