Old God

The Old God was a parasitic, sentient planet that fed on the souls, and therefore the stories, of the inhabitants of the seven neighbouring planets. He was considered to be a great and fearful god.

Biography
He slumbered for thousands of years, until the Long Song ended. Then, he awoke and threatened to consume the seven planets in the system. Eventually, the Eleventh Doctor let him take his memories. The Doctor was then saved by Clara Oswald, who gave the Old God the leaf that told all of her family's story, all that happened, all that didn't happen and all that should have happen. The overload of stories caused him to implode. (TV: The Rings of Akhaten)

Trivia
The Old God somewhat resembles Cthugha, a deity added to the Cthulhu Mythos by August Derleth. It too was a giant ball of fire, easily mistaken for a sun, that was in fact an ancient, sleeping god.