That night, a comet soared across the sky, and his grace tugged fitfully downwards.
Angels, in their most basic form, are much like the stars and comets that spin across the sky, bright and warm and distant. Distance was not an advantage to Castiel's mission, and warmth would only melt so much of the icy depths, and his light would only guide him in the upper rings.
Humans wish upon stars and pray to his Father and the angels, however the stars are the only ones allowed to fall and be worshiped without fear. Castiel unfurled his wings, wide and shimmering like an inky nebula, then hurled himself downwards. Sam Winchester would be the only human to witness an angel fall, but like most humans who spot crashing spot of light, he would believe it was a meteor.
He wished upon it none the less.
Hell was cold and dark, tempting to snuff out the grace of the invading angel as it had done to his light and warmth. It weakened Castiel, yet he pressed forward into the darkness. His grace hummed gently as he searched, beckoning to his target and warning the lesser demons of his presence.
In the deepest and darkest level of Hell, he found it; a small flicker pulsed brightly, pulling him in with it's warm gravity. His grace sighed, offering itself to the bright soul before it. It compliantly nestled itself within the safety of the heavenly presence.
Castiel traveled upwards, gaining back his heat first, then his light, and finally his distance from the pit. Such travel damaged his wings, so he took refuge upon Earth. It would give him the change to look over the little stole taking harbor within his grace. This was Dean Winchester, so bright and warm and heavenly, almost an angel were it not for the obvious human trait that tugged at the angel's grace forcefully.
Humans, unlike angels, are so very close. The threat of closeness startled and intrigued the angel. It felt like a small star pulling him to melt against it's warmth, and as much as Castiel desired to hold and examine it a little longer, his task was to return this soul to a human body. A human can be crafted from most anything: a bit of will, some earth, old and dead parts of other humans, but Castiel found his material a bit higher up. The angel plucked just a bit of a star and shaped it around the soul, forming a human male a little over six feet tall and broadly built with bright green irises beneath his closed lids. By now, his wings were repaired enough to return to Heaven, and he spread them once again in preparation to leave.
Dean's heart started to thump in his chest.
Castiel turned, grace sighing again in wonder, and approached this still bright sun in the pitch black of the forest.
'Just once more.'
He slid a hand over the man's left bicep, quickly pulling away when his grace singed the freshly created skin. Oh, how fragile and warm and beautiful and close! The angel could spend all night with this man who urged him nearer to his very core, however he had so many matters in Heaven to attend to now that Dean was back on Earth. Castiel took his leave, shooting upwards.
Sam spotted another comet about a year after Dean's death. Quietly, he smiled to it as he hopped into the Impala.