He was looking for an eagle, or perhaps one of the other strange creatures who roamed these lands. Sirius had never seen an eagle in person before, or many birds at all for that matter. They had always been out of reach, too far beyond the walls of the aviary, always disappearing over the horizon when they were let out for training. He had always watched them go enviously; there were no tethers to keep them in place, no chains to drag them back home.
One day he had tried to fly after him, when they had first let him into the air. They had been so close at the time - he was convinced that if he tried hard enough, if he beat his wings fast enough, he could catch up to them. He didn’t know what he would do once he did, if he did; but in the end it didn’t matter. His captors were bigger and faster than he was, and he was caught before he got even twenty feet into the air.
Nor did they believe him, when he promised he wasn’t trying to escape. I just wanted to see the birds.
But that was in the past - now Sirius was as free as those birds he’d watched jealously. The entire land and sky stretched out before him, farther than his eyes could see. There were no pegasus guarding him, ready to steer him back to his group. There was no ropes tethering him to the ground.
Free.
He scanned the landscape below, looking for movement across the snowy plains. It seemed he was the only bird in the sky today - the horizon was empty as far as he could see - but neither was there a creature to break up the empty expanse on the ground. It was as if winter had chased all the life from the land, and even with the incoming spring the animals were loathe to return.
So he drifts lower and lower, low enough to see the individual stalks of wheat grass bending in the breeze, and finally he sees something moving.
He flares his wings, changing directions on a whim to soar towards the sleek creature. He thinks it a strange deer at first, tall and pale and unusual. But as his hooves touch the ground, and he stumbles into a canter, he realizes it’s just another horse - a strange horse, but a horse all the same.
“Sorry!” he calls breathlessly, skidding to a stop some distance away. His dark wings spread to either side of him, buffeting the stranger with their wind as he struggles to slow himself. Sirius tosses his head back, nearly sitting to slow his momentum. "Sorry - I thought I could stop faster." He'd blame the snow; he didn't have much practice landing on an icy or sloshy terrain, after all.
moon dust in your lungs,
stars in your eyes,
you are a child of the cosmos,
a ruler of the skies
@Maximus ! notes