"This must be a simply enormous wardrobe!" thought Lucy, going still further in and pushing the soft folds of the coats aside to make room for her. Then she noticed that there was something crunching under her feet. "I wonder is that more moth balls?" she thought, stooping down to feel it with her hands. But instead of feeling the hard, smooth wood of the floor of the wardrobe, she felt something soft and powdery and extremely cold. "This is very queer," she said, and went on a step or two further. (1.23)
The first great transformation in the book is the slow transition from our world to Narnia as Lucy keeps walking further and further back into what seems to be a never-ending wardrobe!
Wrong will be right, when Aslan comes in sight, At the sound of his roar, sorrows will be no more, When he bares his teeth, winter meets its death And when he shakes his mane, we shall have spring again. (8.18)
Aslan's presence will shake up and transform everything in all of Narnia, from the weather to ethics to feelings.
"I've come at last," said he. "She has kept me out for a long time, but I have got in at last. Aslan is on the move. The Witch's magic is weakening." (10.36)
When Father Christmas appears in Narnia, it is a sign that time has begun to pass in a normal way again. The endless winter is being transformed into normal, human, cyclical time with landmarks like holidays.
Every moment the patches of green grew bigger and the patches of snow grew smaller. Every moment more and more of the trees shook off their robes of snow. Soon, wherever you looked, instead of white shapes you saw the dark green of firs or the black prickly branches of bare oaks and beeches and elms. Then the mist turned from white to gold and presently cleared away altogether. Shafts of delicious sunlight struck down onto the forest floor and overhead you could see a blue sky between the tree-tops. (11.30)
The entire land of Narnia is changing in response to Aslan's presence. Think of it as time-lapse photography in the real world for a whole country.
They had been just as surprised as Edmund when they saw the winter vanishing and the whole wood passing in a few hours or so from January to May. They hadn't even known for certain (as the Witch did) that this was what would happen when Aslan came to Narnia. But they all knew that it was her spells which had produced the endless winter; and therefore they all knew when this magic spring began that something had gone wrong, and badly wrong, with the Witch's schemes. (12.2)
Like Edmund's transformation from traitor to hero, the switch from winter to summer in Narnia is virtually instantaneous, with no real spring or intermediate stage in-between.
"Hand it to me and kneel, Son of Adam," said Aslan. And when Peter had done so he struck him with the flat of the blade and said, "Rise up, Sir Peter Fenris-Bane." (12.27)
Aslan knights Peter in order to recognize his transition from boy to warrior. The actual knighting ceremony doesn't cause the transformation – it just makes it official.
The rising of the sun had made everything look so different – all the colours and shadows were changed – that for a moment they didn't see the important thing. Then they did. The Stone Table was broken in two pieces by a great crack that ran down it from end to end; and there was no Aslan. (15.25)
History, the law, and the Deep Magic from the Dawn of Time all transform in the wake of Aslan's great sacrifice.
There, shining in the sunrise, larger than they had seen him before, shaking his mane (for it had apparently grown again) stood Aslan himself. (15.29)
Aslan isn't quite the same after his resurrection. He seems a little bigger, a little brighter, and little more energetic. He has been renewed and strengthened by his terrible experience.
I expect you've seen someone put a lighted match to a bit of newspaper which is propped up in a grate against an unlit fire. And for a second nothing seems to have happened; and then you notice a tiny streak of flame creeping along the edge of the newspaper. It was like that now. For a second after Aslan had breathed upon him the stone lion looked just the same. Then a tiny streak of gold began to run along his white marble back – then it spread – then the colour seemed to lick all over him as the flame licks all over a bit of paper – then, while his hind-quarters were still obviously stone the lion shook his mane and all the heavy, stony folds rippled into living hair. (16.5)
Breath is often metaphorically associated with the spirit and with holy things, and Aslan's breath has incredible transformative powers.
And they themselves grew and changed as the years passed over them. And Peter became a tall and deep chested man and a great warrior, and he was called King Peter the Magnificent. And Susan grew into a tall and gracious woman with black hair that fell almost to her feet and the Kings of the countries beyond the sea began to send ambassadors asking for her hand in marriage. And she was called Queen Susan the Gentle. Edmund was a graver and quieter man than Peter, and great in council and judgement. He was called King Edmund the Just. But as for Lucy, she was always gay and golden haired, and all Princes in those parts desired her to be their Queen, and her own people called her Queen Lucy the Valiant. (17.21)
Although each of the Pevensie children undergoes a transformation to adulthood at the end of the book, all of these transformations will be reversed when they go back to England.