I've been trying to get the 'look' of the snow-unicorns nailed down in my head.
Hiran had seen the High One's army once, and thought them a wondrous, impressive sight, with their glossy dark horses and the long-legged dogs that strode obediently at their heels. They had been dressed in fine clothes and had weapons at their sides, great sweeping swords with jeweled hilts. They had laughed and joked with each other, and sat astride their metal-decked horses, and Hiran had been certain that he would never see anything so amazing again in his limited life.
When the Northlanders rose over the hill, the boy had to sit, knees too weak to hold him, his jaw felt disconnected from his head, and his eyes after a moment grew dry and irritated as he forgot to blink. The High One's army had in a moment been reduced in his memory to so much dust in the wind.
They were a dance of glory, a collection of beauty so amazing and unbelievable that Hiran could not credit what his eyes told him. They were unicorns. Not delicate, slight-boned, retiring creatures with big soulful eyes like the pictures in his texts. Not anything like the white horses with false single-spiral horns that played the part in the summer festivals.
They were tall. So tall that at first Hiran did not notice the colorfully clothed riders that sat upon their shoulders. They were not white. Or rather, they were not only white. They were white, and gray, and brown, and black, and golden, and a few were nearly blue, like the little cat that stole food from the back kitchen window. They were speckled, and striped, and calico, and had thick ruffs where a horse would have a mane, and long lashing tails. Their coats rippled in the wind, healthy and glossy and rich, cascading over their great feet. They had graceful, arched necks, and upright furred ears, and long, fierce-looking heads with dark restless eyes. From the middle of their broad foreheads twisted double-spiral horns in colors as varied as their coats.
They moved at a long-legged walk, and one or two of them danced ponderously in their tracks. Hiran could hear them, as they grew in his vision, the stamp of their hooves in the packed dirt, and the sound of them calling to each other. They did not snort and blow like horses, they rumbled, like a deep purr, and occasionally raised their heads and called, a great ringing sound between a roar and a huntingbird call.