Aslan is a character who appears in each of the seven Chronicles of Narnia books, including the first to be written, The Lion, the Witch, and the Wardrobe. Also known as "the Great Lion," and the "Son of the Emperor-Over-the-Sea," Aslan is a talking lion and the guardian of the mythical land of Narnia. The author of these books, C.S. Lewis, described Aslan as a Christ-figure, showing the form Christ may have taken if he had been sent to a different world than ours.
Throughout the seven books in the series, the Great Lion interacts with a variety of characters, both human and otherwise. Many of these characters are taking animals, while others are magical creatures or humans — mainly human children. In the first book written, The Lion, the Witch, and the Wardrobe, the dwellers of the land of Narnia are anticipating the return of Aslan in the midst of the tyrannical reign of the evil White Witch. He does return, and defeats the White Witch, but not in the way that anyone expects.
Instead of taking over by force, Aslan allows himself to be captured and killed, later rising from the dead. This is a direct parallel to the Biblical account of Jesus' death and resurrection. According to the two stories, both Jesus and his Narnian counterpart were expected to defeat the reigning powers by force, but both allowed themselves to be killed, disheartening their followers for a time. These deaths, however, fit various prophecies and statements made earlier.
There are many other events in the various Narnia books that are taken from the accounts of Jesus' life in the Bible. Aslan is referred to as the Son of the Emperor-Over-the-Sea, a god-like figure. A version of the end of the world is shown in The Last Battle, heavily influenced by descriptions of the New Jerusalem in the book of Revelations. In The Last Battle, it is clear that the characters die as the world is ending, only to be brought to a new world, where they can choose to go with Aslan or remain in darkness.
In addition to mirroring the events of Jesus' life, Aslan shows many characteristics and personality traits that Christians attribute to Christ. Characters either love or fear him, with those who fear him often attempting to kill or undermine him. His followers are able to talk to him and receive reassurance and peace, even in the middle of desperate situations. Aslan is also able to bring great joy to those who trust him, as is evidenced at the end of The Lion the Witch and the Wardrobe, when he has set the land free from the White Witch and rejoices with the Narnians.