Akhaten, a.k.a. the Old God or the Grandfather, is a living planet-sized entity orbited by a populous system of seven worlds known as the Sun-Singers of Akhet. It feeds on the memories of other life forms and is worshiped as a god by the inhabitants of the seven worlds, who ritually offer him objects of personal emotional value to be consumed.
For thousands of years the Old God has slept, being kept appeased by his Choristers singing a never-ending Long Song. Sometimes, when the song is interrupted, the current Queen of Years must be sacrificed to satisfy the hunger of Akhaten.
When the Eleventh Doctor and Clara Oswald visited the system, they helped to prevent the sacrifice of Merry Gejehl, resulting in the awakening of Akhaten, who threatened to consume the entire system and all its inhabitants. After the Doctor offered him his memories and Clara offered him the leaf which carried with it the story of her family, the Old God was overloaded and finally imploded. Presumably, it either left enough remains for the seven worlds to orbit around, or else the Doctor probably helped the natives to re-stabilize their planets' orbits somehow.
- Doctor Who series 7 - "The Rings of Akhaten" (2013)