En fest för kråkor

Samwell Tarly påminner om att ha läst att Skagosi kör stora, raka unicorns till krig.

Unicorn horns are amongst plunder brought from distant lands by Euron Greyjoy.

En dans med drakar

Jon Snow, in a wolf dream as Ghost, sees that Shaggydog has fought and killed what may be a unicorn:
A wild rain lashed down upon his black brother as he tore at the flesh of an enormous goat, washing the blood from his side where the goat’s long horn had raked him.

In the cave of the three-eyed crow Leaf tells Bran Stark that the unicorns are all but gone.

Among some of the tribute collected from the wildlings passing through the Wall is a helm made with a unicorn’s head.

Bran meets Leaf in the cave of the three eyed crow who tells him that unicorns still exist.

Jon drömmer också att Ghost dödar något som kan vara en enhörning. Även en vildmark bär en hjälm gjord av enhörningens huvud.

Ja

Den närmaste bekräftelsen på detta vi har är Leaf, säger Bran, men vi har också andra källor som hävdar att de finns. Det verkar som om de har fallit i samma rike som de vita vandrare och jättarna, med majoriteten som tror på dem att vara sagor men vissa som fortfarande känner sanningen.

And they did sing. They sang in True Tongue, so Bran could not understand the words, but their voices were as pure as winter air. "Where are the rest of you?" Bran asked Leaf, once.
"Gone down into the earth," she answered. "Into the stones, into the trees. Before the First Men came all this land that you call Westeros was home to us, yet even in those days we were few. The gods gave us long lives but not great numbers, lest we overrun the world as deer will overrun a wood where there are no wolves to hunt them. That was in the dawn of days, when our sun was rising. Now it sinks, and this is our long dwindling. The giants are almost gone as well, they who were our bane and our brothers. The great lions of the western hills have been slain, the unicorns are all but gone, the mammoths down to a few hundred. The direwolves will outlast us all, but their time will come as well. In the world that men have made, there is no room for them, or us."
A Dance with Dragons, Bran III

Det hävdas att Euron Greyjoy använde unicorn horns för att vända folk till sin sak, men det är aldrig sagt om dessa var riktiga eller inte (mer om detta senare)

Aye, he thought, a great victory for the Crow's Eye and his wizards. The other captains would shout his brother's name anew when the tidings reached Oakenshield. Euron had seduced them with his glib tongue and smiling eye and bound them to his cause with the plunder of half a hundred distant lands; gold and silver, ornate armor, curved swords with gilded pommels, daggers of Valyrian steel, striped tiger pelts and the skins of spotted cats, jade manticores and ancient Valyrian sphinxes, chests of nutmeg, cloves, and saffron, ivory tusks and the horns of unicorns, green and orange and yellow feathers from the Summer Sea, bolts of fine silk and shimmering samite... and yet all that was little and less, compared to this.
A Feast for Crows, The Reaver

Davos kallar sig Skagos "unicorns och cannibals" och Sam läser att enhörningar bor där med Dareon, även om de kommenterar att de kan se en.

Nine-and-twenty ships had set sail from the Wall. If half of them were still afloat, Davos would be shocked. Black skies, bitter winds, and lashing rains had hounded them all the way down the coast. The galleys Oledo and Old Mother's Son had been driven onto the rocks of Skagos, the isle of unicorns and cannibals where even the Blind Bastard had feared to land; the great cog Saathos Saan had foundered off the Grey Cliffs.
A Dance with Dragons, Davos I

The island sat at the mouth of the Bay of Seals, massive and mountainous, a stark and forbidding land peopled by savages. They lived in caves and grim mountain fastnesses, Sam had read, and rode great shaggy unicorns to war. Skagos meant "stone" in the Old Tongue. The Skagosi named themselves the stoneborn, but their fellow northmen called them Skaggs and liked them little. Only a hundred years ago Skagos had risen in rebellion. Their revolt had taken years to quell and claimed the life of the Lord of Winterfell and hundreds of his sworn swords. Some songs said the Skaggs were cannibals; supposedly their warriors ate the hearts and livers of the men they slew. In ancient days, the Skagosi had sailed to the nearby isle of Skane, seized its women, slaughtered its men, and ate them on a pebbled beach in a feast that lasted for a fortnight. Skane remained unpeopled to this day.
Dareon knew the songs as well. When the bleak grey peaks of Skagos rose up from the sea, he joined Sam at Blackbird's prow, and said, "If the gods are good, we may catch a glimpse of a unicorn."
A Feast for Crows, Samwell II

Världen av is och eld kommenterar också detsamma som Sam läser om enhörningarna.

The Skagosi who reside there are little regarded by the other Northmen, who consider them no better than wildlings and name them Skaggs. The Skagosi call themselves the stoneborn, referring to the fact that Skagos means "stone" in the Old Tongue. A huge, hairy, foul-smelling folk (some maesters believe the Skagosi to have a strong admixture of Ibbenese blood; others suggest that they may be descended from giants), clad in skins and furs and untanned hides, and said to ride on unicorns, the Skagosi are the subject of many a dark rumor.
The World of Ice and Fire, The North: The Stoneborn of Skagos

Men inte alla mästare verkar tro att enhörningarna var verkliga, men det verkar som nedgången från oförskräckliga köpmän som säljer falska enhörningshorn. Vissa unicornhorn har blivit sedda som verkar vara verkliga eller åtminstone annorlunda än vad som tidigare sett. Även om mästarna ännu inte hittar ett levande exempel eller skelett.

The "unicorns" of Skagos were once scoffed at by maesters at the Citadel. The occasional "unicorn horn" offered by disreputable merchants has never been more than the horn of a kind of whale hunted by the whalers of Ib. However, horns of quite a different kind—reputed to be from Skagos—have been seen by the maesters at Eastwatch upon occasion. It is also said that those seafarers brave enough to trade on Skagos have glimpsed the stoneborn lords riding great, shaggy, horned beasts, monstrous mounts so sure-footed they have been known to climb the sides of mountains. A living example of such a creature—or even a skeleton—has long been sought for study, but none has ever been brought to Oldtown.
The World of Ice and Fire, The North: The Stoneborn of Skagos

Slutligen kan vissa hävda enhörningar hittas i Ib som tycks vara överens med enhörningar från Skagos, som vissa maesters har hävdat att Skagosi har en stark blandning av Ibbenese blod.

Ib is the second largest island in the known world; only Great Moraq, between the Jade and Summer Seas, is larger. Stony and mountainous, Ib is a land of great grey mountains, ancient forests, and rushing rivers, its dark interior a haunt of bears and wolves. Giants once dwelt on Ib, we are told, but none remain—though mammoths still roam the island's plains and hills, and in the higher mountains, some claim unicorns can be found.
The World of Ice and Fire, Beyond the Free Cities: Ib

Observera att den lila unicorn sigilen tillhör House Brax och att de sägs ha bildats från ett äktenskap mellan de första männen och andalsna. Som ett historiskt hus är det troligt att fler enhörningar var omkring när det skapades och därmed sigilen.

A party of mounted horsemen rode forward to challenge them as they approached the stakes. The knight who led them wore silver armor inlaid with amethysts and a striped purple-and-silver cloak. His shield bore a unicorn sigil, and a spiral horn two feet long jutted up from the brow of his horsehead helm. Tyrion reined up to greet him. "Ser Flement."
Ser Flement Brax lifted his visor. "Tyrion," he said in astonishment. "My lord, we all feared you dead, or…" He looked at the clansmen uncertainly. "These… companions of yours…"
A Game of Thrones, Tyrion VII

In time, Lannister kings wed their children to Andals as well; indeed, when Gerold III died without male issues, a council crowned his only daughter's husband, Ser Joffery Lydden, who took the Lannister name and became the first Andal to rule the Rock. Other noble houses were also born in such unions—such as Jast, Lefford, Parren, Droxe, Marbrand, Braxe, Serrett, Sarsfield, and Kyndall. And thus revitalized, the Kings of the Rock expanded their realm still farther.
The World of Ice and Fire, The Westerlands

Vi ser aldrig en förstahandsvisning, men i Kapitel 3 i ADWD Jon drömmer att:

A wild rain lashed down upon his black brother as he tore at the flesh of an enormous goat, washing the blood from his side where the goat's long horn had raked him.

Det kan vara en vision om Shaggydog som dödar en enhörning. Detta stöds av Sams omnämnande i kapitel 15 i AFFC att de personer där Shaggydog är på:

... rode great shaggy unicorns to war. Skagos meant "stone" in the Old Tongue.