This book is about a time before the Pevensie children were born. Digory Kirke, who grows up to become the professor, in The Lion, the Witch, and the Wardrobe, has an Uncle who is a bad magician, a mother who is dying, and a new friend, Polly. Uncle Andrew has been dabbling at magic to transport people between worlds. He is too cowardly to test it himself, and tricks Digory and Polly into testing it for him.
Polly is tempted when Uncle Andrew calls her "a very attractive young lady." She is probably from 10 to 14 years old. This appeals to her pride, one of the seven deadly sins, or her vanity.
Uncle Andrew is tempted to use the children for his own purposes, regardless of any consequences to them. Is he really tempted, in that he has a choice in the matter? I'm not sure. He may be so far gone that he automatically makes bad choices.
Uncle Andrew is tempted by pride, one of the seven deadly sins, to consider himself above all rules:
"Oh, I see. You mean that little boys ought to keep their promises. Very true: most right and proper, I'm sure, and I'm very glad you have been taught to do it. But of course you must understand that rules of that sort, however excellent they may be for little boys--and servants--and women--and even people in general, can't possibly be expected to apply to profound students and great thinkers and sages. . . ."
"All it means," [Digory] said to himself, "is that he thinks he can do anything he likes to get anything he wants." - C. S. Lewis, The Magician's Nephew, New York: Macmillan, 1955, p. 16-17.
He is also tempted, by pride, to sacrifice guinea pigs, Digory, Polly, or anything else, to achieve his goals. When Digory and Polly meet the witch, she has the same kinds of thoughts.
Digory and Polly, in the Wood Between the Worlds, are tempted to explore a world other than their own, just because they can. They do so. They almost forgot to mark their way back. They are tempted to quarrel over almost forgetting this, and do so.
Digory is tempted, apparently out of an insatiable curiosity, to strike the bell in Charn that releases the spell that has kept the witch-queen, Jadis, in a state of suspended animation for a long time, perhaps millenia. This results, eventually, in Jadis coming to our world, London in the early part of the 20th century. It also results in Digory and Polly sending the witch to another world, Narnia, to get her out of London. This is good for our world, but a terrible evil for Narnia. Uncle Andrew, a cab-driver and his horse are inadvertently brought to this world, too.
The witch had been tempted to destroy every living thing on her planet, so that she could survive. She yielded to this temptation:
". . . Then I spoke the Deplorable Word. A moment later I was the only living thing beneath the sun."
"But the people?" gasped Digory.
"What people, boy?" asked the Queen.
"All the ordinary people," said Polly, "who'd never done you any harm. And the women, and the children, and the animals."
"Don't you understand?" said the Queen . . . "I was the Queen. They were all my people. What else were they there for but to do my will."
"It was rather hard luck on them, all the same," said he.
"I had forgotten that you are only a common boy. How should you know about reasons of State? You must learn, child, that what would be wrong for you or for any of the common people is not wrong in a great Queen such as I. . . ." - C. S. Lewis, The Magician's Nephew, New York: Macmillan, 1955, pp. 54-55.
Uncle Andrew is tempted not to believe that Aslan is a rational, moral being, able to speak. He yields to this temptation:
Now the trouble about trying to make yourself stupider than you really are is that you very often succeed. Uncle Andrew did. He soon did hear nothing but roaring in Aslan's song. Soon he couldn't have heard anything else even if he had wanted to. And when at last the Lion spoke and said, "Narnia awake," he didn't hear any words: he heard only a snarl. - C. S. Lewis, The Magician's Nephew, New York: Macmillan, 1955, pp. 112-113.
Digory is tempted to get an apple from the garden of the phoenix in a way that he shouldn't. He is also tempted by the promise of immortality which might come from eating such an apple. The witch does yield to this temptation. Digory doesn't. Because he doesn't, Narnia is protected from the witch for many years, his mother is healed of a fatal illness, and the Wardrobe, which is one of the gateways that connects the two worlds, is eventually built from a tree which grew from the core of the apple that cured Digory's mother.