In The Lion, the Witch, and the Wardrobe, it is revealed he had been kept at bay by the White Witch, who had taken over Narnia and cursed it into a Never-Ending Winter without Christmas, and that only two sons of Adam and two daughters of Eve could defeat the Witch and restore Narnia to peace and tranquility.
When the witch's power began to weaken, Aslan was finally able to return, and tasked a fox with gathering troops for the upcoming war against the witch and her evil forces. It wasn't long before the Pevensies, minus Edmund, had come to Aslans camp where they met the majestic lion.
Aslan had a private talk with Peter, giving him encouragement and advice, when they heard the call of Susan's horn, alerting them that the girls were in danger by Maugrim who met his end by Peter's sword, a brave act for which he was awarded by Aslan with Knighthood, naming him Sir Peter Wolfsbane.
He sent some soldiers to follow Maugrim's follower to recover Edmund from the Witch's capture and when they succeeded, Aslan had a talk with Edmund about his past offenses, making the boy see the error of his selfish ways, especially after Edmund had seen the consequences his actions had on others.
However, the Witch came to Aslan's Camp, demanding Edmund's life per the law of Narnia stating every traitor's life belonged to her in accordance to the Deep Magic on which Narnia was built, threatening unless she had blood as the law demanded, all of Narnbia would perish in fire and water.
Aslan and Jadis shared a private word in his tent. When the emerged, he announced the Witch had reannounced her claim on Edmund's life but unknown to everyone, at a terrible cost.
Aslan snuck out of the camp but was followed by Susan and Lucy whom he allowed to accompany him for a while but told them to go back before it was revealed that Aslan had willingly traded his life for Edmund's and had come to the Stone Table o be willingly sacrificed by the White Witch.
As he approached, Aslan was jeered and mocked by the Witch's forces, knocked down by Otmin, the General of the Witch's army, and had his mane shaved to further humiliate him before he was roped and binded and dragged onto the table where Jadis bent down to mock him before scoffing as she then stated, "So much for love..."
As he lay on the table, moments before his death, Aslan saw that Lucy and Susan had not left before they bore witness to the "Great Lion"'s Death by the Witch's hand.
After the White Witch and her army left for battle, Lucy and Susan approached the lifeless body of Aslan and cried into his fur as mice chewed off the ropes binding him. The news of Aslan's death was delivered to Peter and Edmund by a Dryad, convincing them to go to war.
In the morning, Susan and Lucy sadly decided to leave but felt the Stone Table crack and gasped to see Aslan's body gone. But as the sun rose, they saw so that Aslan had risen from the dead. They embraced the lion who explained that there was Deeper Magic, that when a willing victim who had committed no treachery is killed in the traitor's stead, the Stone Table would crack, and even death itself would be reversed. Susan and Lucy urge Aslan they must help Peter and the others, and Aslan tells them to get on his back before he lets out a mighty roar. With the two sisters on his back, Aslan ran all the way to the Witch's castle, empty of all but the Witch's poor victims who'd been turned to stone, including Lucy's friend, Mr. Tumnus the faun whom Aslan brings back to life by breathing on him, and proceeds to do so with the rest of the petrified victims to be rallied as reinforcements.
He leads them all to the Battle of Beruna, turning the tide against Jadis and her forces, and Aslan charges into the fray and finds the Witch about to kill Peter. He makes it in time, saving Peter's life as he pounces the Witch. They stare into each other's eyes for a moment before Aslan mauls her to death, proclaiming to Peter, "It is finished."
At the castle, Cair Peravel, Aslan oversees the Pevensies' Coronation, proclaiming them all Kings & Queens of Narnia, before he vanishes. Though Lucy was sad to see him go, Mr. Tumnus promises her they'll see him again, that one day Aslan will be there and the next day he won't be, coming and going as he is not a tame lion but good.
- Aslan's name is Turkish for "lion".
- Aslan was C. S. Lewis' representation of Jesus Christ. Many parallels exist between the two. For one, Aslan's death and resurrection refers to Jesus's crucifixion and resurrection. Also the reasons are parallel; Aslan died to save Edmund while Jesus died to save people from their sins. Another one is their home; Aslan resides in Aslan's Country while Jesus resides in Heaven.
- In the Apocrypha of the Bible in Esdras 2, there's a lion who speaks like man during the seer's vision of the eagle.
- After being approached for the role, actor Liam Neeson went on a safari with his family to study the lions and to figure out why they are called the kings of the jungle. He also did this in order to find a fitting voice for Aslan.