Narnia: The Magician's Nephew.

Before the wardrobe, before the Pevensies, there was the creation of Narnia itself. In 1950s London, two children, Digory and Polly, are tricked by Digory’s eccentric Uncle Andrew into a journey between worlds using enchanted rings. After accidentally awakening the powerful and ancient Empress Jadis in the dying world of Charn, they flee to a void that is suddenly brought to life by the song of a great lion. As a new world is born, the children must protect it from the darkness they unwittingly brought with them