Faërie Imagery
Much of Tolkien's argument in this essay revolves around Faërie, the mysterious land of the imagination where all true fairy-stories are set. It is impossible to directly describe this "perilous realm," but the indirect descriptions are beautiful and full of Faërie imagery. For example, Tolkien describes the land of fairy-stories as "wide and deep and high and filled with many things: all manner of beasts and birds are found there; shoreless seas and stars uncounted; beauty that is an enchantment, and an ever-present peril; both joy and sorrow as sharp as swords." Such fantastic imagery permeates the essay in an attempt to capture the spirit of Faërie without directly defining it.
Eucatastrophe Imagery
Tolkien defines the primary element of consolation in fairy-stories as the "sudden joyous turn" from darkness to light, or the eucatastrophe. Just as it seems that evil will triumph, good suddenly emerges victorious in a glorious role reversal. This imagery is striking, especially in context of Tolkien's own work; in The Lord of the Rings, Frodo hesitates at the last moment, tempted to keep the Ring for himself, but suddenly Gollum's greed leads to the destruction of the Ring and the ultimate defeat of evil, revitalizing the land and purging Middle-Earth of corruption. Tolkien also draws a parallel to the eucatastrophe of human history: Jesus's birth and resurrection.
Recovery Imagery
Another aspect of fairy-stories that Tolkien finds essential is the quality of recovery, or "a recovery of clear sight." This is a particular quality of fantasy that consists of an artistic twist on reality that makes the reader wonder anew at the strangeness and beauty of his own reality in the primary world. For example, if in a fairy-story the grass is a stunning blue, when the reader returns to "the real world" he is struck by the beauty of the green grass, realizing its strangeness and wonder again. This effect can also be achieved by merely viewing the primary world through a lens of mystery and wonder, as in Chestertonian fantasy, but Tolkien argues that only fairy-stories can perform it most effectively.
Christian Imagery
Tolkien is a Christian, and there is accordingly quite a bit of Christian imagery throughout this essay. He refers often to the Creator, whom we emulate when we create things ourselves, resulting in our acts of "sub-creation." The Epilogue is particularly full of Christian imagery, referring to such eucatastrophic events in human history as the birth of Jesus Christ, and later his glorious resurrection from the dead. These two events are the "sudden joyous turns" of the entirety of human life, and it's clear that these images have enormous significance for Tolkien.
