Setting: Post movie-verse, incesty Elsanna. I'll be doing some world-building, too.

Credit: The idea for this fic came about when I said to my friends, "Frozen fic idea: GRRM's ice zombies come to Arendelle and Elsa kicks ice zombie ass." And friends said I'D READ THAT. So this isn't Westeros, but there will be ice zombies. And royal sibling incest. (Don't worry, though, you won't need to have read A Song of Ice and Fire or seen Game of Thrones to understand anything.)

The title, "The Burning Circle of Our Days," is adapted from William Butler Yeats' poem The Two Trees.

Elsa did not dream.

She never had. And for many years she hadn't known there were such things as dreams that lived in the depths of sleep. Her parents had never told her about them. Perhaps it had simply never occurred to them that Elsa would be different in that way, too; perhaps it had been yet another measure of concealment. But until she was grown, Elsa thought "dreams" was only the word for the wishes of your heart.

But then she read—some time in the endless, empty days after she'd lost her parents to the sea—about dreams that came to you when you slept. Years later, when they no longer did-not-speak through closed doors, she asked Anna if she had that kind of dream.

"Oh, sure," Anna said, digging into a strawberry tart. "I had one last night that I was riding on the back of a flying horse. Do you think there are really flying horses?"

"Possibly." If there were dreams you only had when you were sleeping, there could easily be horses that flew. "Do you dream often?"

Anna had icing on the tip of her nose. "Every night, mostly. Do you—you've really never dreamed?"

She looked curious, rather than fearful, but anything that set Elsa apart touched her own heart with unease. She shook her head as she wiped the icing off Anna's nose, feeling herself smile when Anna grinned at her. Her heart beat hard, twice, in her chest, and she wondered what it meant that she did not dream at all.

Never. Not once. From the moment she slipped into sleep to the moment she woke, the world of her night was dark—not empty like a void, but calm and peaceful like black water beneath a starless sky.

Why did she not dream? Was it to do with her magic? Did her powers block them out?

"We'll ask Kristoff's family," Anna suggested brightly. But when they'd driven their sleigh, with Anna bundled up against the early spring frost, to the snowy grotto, the trolls said they had never heard of anyone who did not dream—though, they admitted, it had been a long time since they had met a human who could shape the powers of the earth. And the last time they had, they hadn't thought to ask him about dreams.

Elsa knew whom they were talking of and distracted Anna with the promise of hot chocolate back home. He was best left forgotten by those who knew of him and unknown to those who did not.

Especially to Anna.

Elsa began sending for books from every kingdom nearby, and increasingly from those farther and farther away: books on dreams and magic and sleeping; books that were as dry and dusty to the mind as to the touch; books that held no answers at all.

"Maybe you just don't remember dreaming," Anna said, looking the books that spread across every surface in Elsa's study—tables, chairs, floor, even the windowsill. A glint of disquiet in her eyes made the parchment beneath Elsa's fingers crackle with frost.

"There's a lot I know I don't remember," Anna went on, picking up a book in Maldonian and (unknowingly) looking at it upside-down. "And they're really very silly, anyway—last night I went swimming with a herd of pink elephants. Do you think there are pink elephants, really?"

"Maybe." It was hard not to smile when Anna asked questions like that. Elsa delicately closed the book she'd nearly frozen. "What will you dream of next? Pink elephants that can fly?"

Anna's smile was quick, touched with relief. "Maybe."

"Where do you go?" Elsa asked her. Anna blinked. "In your dream—where do you fly?"

"Sometimes I fly over the mountains—sometimes over the sea—I see things I've read about, or that are in the paintings. . ."

Anna started telling Elsa about all her dreams after that. It soothed Elsa's inchoate fears, somehow, to hear of Anna's dreams when she did not have her own.

Gradually, the books were taken off the tables and chairs and windowsills and sent to line the shelves of her study and the library. Her nights stayed dark and peaceful, but before she slept she thought of Anna flying over fjords and forests, into the living sky. She found a different kind of peace in that. If only one of them had to dream, it was better that it was Anna, whose heart was full of light and warmth. What if Elsa's dreams were lonely and dark and jagged like spears of ice?

And for a time, everything was well.

Until Anna had a nightmare.

"Elsa?"

Elsa was awake in one moment to the next, like Anna's half-whisper had the weight of a shout.

Anna stood next to the bed, clutching her dressing gown closed, holding a candle that snuffed out when Elsa looked at her. She would rather have the power of ice than of fire—ice could thaw, whereas ash could not be made whole again—but sometimes it would be more convenient to light a candle on a whim.

But if she could snuff a candle with one stray beat of her heart, she did not want to think about the power of fire.

"What is it?" Now she could see Anna only by the light of the moon. Pushing back the covers, she reached for the matchbox she kept in her bedside table. The match, though, snuffed out as soon as it was lit. Elsa made a frustrated noise.

"Here, I'll do it," Anna said, and even in the feeble light Elsa could hear the smile in her voice.

Anna lit both their candles and set hers beside Elsa's on the bedside table. Then she perched on the edge of the bed and fidgeted.

"What is it?" Elsa repeated, when Anna only kept wrapping a stray thread, come loose from her dressing gown's embroidery, around and around and around her finger.

"I. . . had a bad dream."

Elsa blinked. "A nightmare." She'd always known about nightmares, too, even before she knew that wasn't a term only for what you feared would come to pass.

"Yeah. . . just a stupid one, though." Anna smiled again, or something like it, but Elsa knew she had her own way of concealing.

Elsa frowned. "What happened?"

"I. . ." Anna started winding the thread faster. "Nothing."

Elsa tried to keep her voice gentle. "It can't be nothing or you wouldn't have come."

Anna peeped at Elsa past the unmarred hair that fell over her eye. "Well, that's the important thing, isn't it? That I came here."

Elsa was confused. "Is it?"

Anna nodded fervently, twisting the loose thread so that part of the design popped loose. "So—so the dream isn't important, it's what happened after I. . . woke up from it. You see?"

On the beside table, the closest candle guttered, then went dark. Anna pressed her lips together.

"Elsa. . ."

"You had a nightmare about me."

"No," Anna said forcefully. "Not about you, about. . . a winter that wouldn't end. I read it in a book, that's all! Elsa—"

Ice was whispering across the sheets, up the posters of Elsa's bed, chipping down from the canopy. Control it, control it—Elsa thought, but she saw the moonlight shattering on the icicles, and when Anna breathed out her breath clouded the air. . .

Anna grabbed her hand. Elsa's heart twisted as she imagined the ice traveling up Anna's arm and across her face, and she tried wrenching herself away, but Anna wouldn't let go. She tried to shake her other hand free of her dressing gown so she could hold on with both hands, but the thread was wrapped around her finger so that she couldn't get it loose.

"Oh, butternut fudge!" she cried, and the picture she made was so silly, with her hair tufted out of her braid like that and her finger caught in her own dressing gown, that some of the panic in Elsa's chest thawed.

"Which book was this?"

"It was something about the history of Arendelle. I found it in your study. You don't read stuff like that all the time, do you? Because it was pretty bleak, and if you're always reading stuff like that it's no wonder that you. . . um. . ." She glanced at the bed, whose tall, sturdy frame glittered in the silver light.

Elsa did not feel capable of thawing it yet, so she ushered Anna into her sitting-room and shut the door on the cold.

"A History of Magic in the Wild North?" she asked calmly as Anna untangled her finger from her dressing-gown.

"Probably. It was full of some rather nasty people." She frowned, and Elsa thought that if the author of that book had still been alive, Anna might have sent him a strongly worded but very polite letter that he ought to write something a bit nicer. "Surely you've got to have some books on good magic."

"It's a history book, Anna. Good deeds are rarely recorded in them."

Judging by Anna's expression, she was going to spend tomorrow afire with the ambition to become a historian who wrote about only nice things (until supper intervened and her attention was caught by dessert).

"And magic. . ." Elsa wanted to shiver, but years of training repressed it. Cold never bothered her, but there were things more paralyzing than ice. "Magic comes with a price."

Anna looked at her, for once not biting her lip or wringing her hands. It was a serious, grown up look; a reminder of the price they had already paid.

"A price," Elsa said quietly, "that you have to keep on paying."

Elsa wasn't far off the mark.

The next day, Anna dragged her to the library, a large, airy, open room their father had had newly built for her as a gift for her thirteenth birthday, to try and ease her loneliness. To an extent, it had worked. The high ceilings and rows of windows that ran from floorboards to eaves had given her a room full of light, and the books had, for a time, breathed companionship into her life. But it had not lasted. Any book worth being read would at some point make your eyes turn from the page and seek a view of the outside world, wondering if the same adventures lay beyond the glass, waiting for you to find them. In the end, every book in this endless, empty, echoing room had been a reminder of what she could never have.

Anna cleared her throat. Without realizing it, Elsa had drifted to the windows and stood looking across the fjord, toward the horizon, her breath crystallizing on the glass. Turning, she tried to school her expression. . .

And lost the battle at the sight of Anna striking a triumphant pose in front of a governess' board on which she had pinned a large, blindingly pink banner:

The Good Things Magic Can Do!

"Right," she said, her expression alight with the mix of determination and zeal that she normally reserved for chocolate-on-chocolate cake with strawberries. "This is what's going to happen. I'm going to fill up this board! You watch me."

Elsa had read every book in the castle—the library, her parents' studies, and all the volumes she'd added since becoming queen. She knew there was nothing like what Anna was looking for. Magic was dark and dangerous, a temptation to evil, an imbalance of the natural order. The only good that had ever come of it had been due to Anna, when Elsa had wanted to delight her. Perhaps other sorcerers, the ones who had not made it into the books as conquerors or eaters of children or enslavers, who had not been driven from their homes by hatred—perhaps they had had their Annas. But building snowmen and ice-skates for your little sister wouldn't make it into books.

Still, Elsa's heart seemed suddenly too small for the fondness inside it.

"Wouldn't you rather go skating?" she asked. "Or we could have a snowball fight—through the whole castle."

Anna's face lit up, but then she pursed her lips and shook her head. "No no no no, no. This is important, Elsa. Magic isn't bad, it's being scared of things that's bad for you."

There is beauty in it, but also great danger. "Magic makes things. . . more," she said quietly. "More dangerous. More fearful. It's easier to do damage with magic."

"Then it's easier to do good, too," Anna said firmly.

Elsa saw that she would not convince her. But she couldn't watch Anna rifle through book after book, finding nothing like what she believed, only endless reports of treachery and terror.

So she excused herself, burying the pang she felt when Anna's face fell—frosting the doorknob as she let herself out—and went to the kitchens instead. She asked the cook if she wouldn't prepare Princess Anna's favorite strawberry cake with chocolate icing for dinner that night.

Anna would need a lift, after being so disappointed. Elsa had had years to understand the danger she herself posed.

Anna. . . had not.

There was a difference between being hurt once, and knowing it could happen again.

But Anna did not come up for dinner.

Elsa ate alone at the table spread with untouched dishes, the moonlight of early autumn glittering on the frost that spread across the cloth. She stopped the ice before it covered Anna's cake, but let the rest of the food freeze solid.

When she had eaten all she could of her cold soup, she stood, picked up the cake plate, and left the informal dining room for the library. The lamps struck notes of brightness in the depths of shadow and silver, and in a pool of buttery-yellow light, she found Anna, surrounded by towers of books.

And sleeping, using a book as a pillow and drooling a bit on the page.

Feeling herself smiling, Elsa set the cake down on the table and brushed Anna's bangs back from her face. Anna's eyes fluttered open. She smiled sleepily when she saw who it was, and then scrunched her nose.

"Ow," she said as she raised her head, wincing. "When'd I fall asleep?"

"I don't know. You missed dinner. But I brought you the most important part."

"Dessert?" Anna brightened when she saw the cake, the chocolate decorated with strawberries and whorls of pink icing. "Ooh, that's my favorite!"

"I know."

Elsa moved the books and scrolls out of the way as Anna dug in, not even bothering with the extra plate Elsa had brought. If ice was Elsa's power, Anna's was the ability to get chocolate absolutely everywhere.

Elsa recognized a lot of the books Anna had brought down: not histories, but the stories of the sort you told children, with trolls, fairies, mermaids, selkies, and dragons; stories of the making of the earth and sea and sky; men that changed into bears, foxes that trapped you with tricks and riddles, the sacred herds of immortal beings; women who turned into owls and feasted on the flesh of the dead and of harpies that hounded the guilty unto madness.

"I thought you would be looking at history," Elsa said, surprised.

"I thought I'd learn about what magic was like, first. Strawberry?" She held one out on a chocolatey fork.

Elsa picked it off the tine and bit it in half, savoring the chocolate. She flipped through the storybook, lingering on the watercolor of mermaids streaming on their backs beneath the surface of the water.

"This reminds me of tales I've read about the afterlife," she said. "How some peoples believe it is an ocean. The souls of the dead swim forever, unable to find shore."

She glanced up at Anna, to see how she was taking this morbidity, and saw that for some reason Anna had gone bright red.

"You're not choking, are you?" Elsa asked, alarmed.

Anna shook her head rapidly. "N-no," she said, stuffing another bite of cake into her mouth. "Ei'm finef."

"Did I upset you?"

Anna shook her head even harder. "Fine," she wheezed. "You're—fine. Um. That's—interesting, about the dead people. I. . . don't think I'd want to go swimming there."

Elsa smiled slightly and finished her strawberry. "No."

"Um," said Anna. "Um. I did—look at this one. History book, I mean. About—about the royal family in Arendelle."

She was blushing, her eyes darting from Elsa's shoulder, then across the room, then back to Elsa's hairline, then up to the ceiling.

"Ah." The moonlight, the lamps, shone suddenly too bright. Elsa closed her eyes.

"You've—read that one before?" Anna asked, her voice a bit higher than normal.

"Yes." She tried not to breathe. "You mentioned the man last night. The one who was. . . like me."

There was a pause. When Anna spoke, she sounded. . . confused? "The—oh! Right, yes. Um. I—couldn't finish that one. It was. . . too horrible. What happened."

What he did, Elsa thought.

"But no, I was talking about. . . um." Anna shifted, her chair creaking. "The, er, the way the royal family, er. . . used to marry, um. . ."

When Anna's words gave out, Elsa finally opened her eyes. Anna's face was so red that she immediately understood.

"The marrying of brothers and sisters?" (Anna nodded jerkily.) "You didn't know?" (She shook her head so hard that her braids flapped.) "Well, it was a very old practice. In the beginning the kingdom was very weak, after all, and they intermarried to keep bloodlines pure and outsiders from gaining influence."

"Er," Anna said. "Ah. Why'd—they stop?"

"It was after the same man we were talking of. Kleykir. The one with powers like mine." Elsa felt the arms of her chair starting to chip with ice. "The one who. . ."

Anna put her hand over Elsa's and squeezed. Her hand was warm and her grip was firm, and if she was still blushing a little, her gaze was steady and her smile did not waver.

"The one who tried usurping his brother's crown," Elsa said. She felt the ice receding, as if Anna's touch had the power to thaw it. "Is any of this familiar?"

"A bit." Anna frowned. "I seem to remember Bera—that was my tutor, you know—saying we don't talk about him? Or don't say his name—or something."

"Correct. Kleykir isn't his real name. He was the Disgraced."

Anna was looking at her in that serious way again. Her fingers curled around Elsa's, until she turned her palm over so that they were holding hands, rather than Anna simply holding onto hers.

"When did you learn about him?" Anna asked quietly.

"In a book that Father did not know held any mention of him. He was careful to keep all of that away from me." She remembered turning the book to ice and breaking it in half, demanding he bring her every book he had hidden about Kleykir the Disgraced, the terrible man who'd been just like her. "He and Mother. . . didn't want me knowing. But when I found that one whisper of him, I knew I had to hear the whole. Father hunted up every scrap of knowledge about him, for me. It was not much. What little was kept was in the event of. . . a child like me being born."

Anna's searching look was almost suspicious. "Do you mean a child with ice powers, or a child who might grow up like him?"

"It makes little difference—"

"It makes all the difference." Anna gripped her hand harder. "Elsa, you ran away rather than hurt anyone. The winter happened because you didn't know how to control it, but now you do. He froze Arendelle so his brother would have to give up the kingdom to him—isn't that what the magic book said? He froze the kingdom so badly that hundreds of people died within a few hours."

Elsa remembered. She didn't dream, but the words penned by stoic historians had writ themselves on her mind, so that if she closed her eyes, she could still see them.

"I didn't have to threaten anyone to become queen."

Anna looked incredulous. "Right. You have all the power in the world—more than he did. You have magic, and you're a queen. You could do whatever you want! And what you do is read books and sit on council meetings and build snow forts with me and make sure everyone has enough food and firewood and blankets during the winter so they never go hungry and cold. Do you think that awful man would have done any of that?"

Elsa couldn't help smiling at the burning indignation in Anna's face. "As he's been dead for three hundred years, I don't suppose I could ask him."

"Well, I bet he wouldn't have. You don't try to kill someone and take their kingdom because you want to do nice things for people." A shadow passed across her face; a memory almost a year old. It was Elsa's turn to squeeze her hand. It chased the shadow away, or at least gave Anna the strength to hide it.

"You were asking about the family intermarriages," Elsa said, to take her mind off that.

"Oh." Anna went strawberry red again. "Yeah. That, um. Surprised me."

"They were discontinued after that. Well, the surviving brother didn't have any sisters, so he had no choice. He married a princess from another kingdom, and things were quite different there. She was horrified at the idea of her children intermarrying. He met some opposition for discontinuing the tradition, but influential members of his council stood in support of his children finding other spouses. They wondered if his brother's evil hadn't been a sign to put an end to the tradition. In the end, King Vortigen left the decision to his children."

"And they married other people?"

Elsa nodded. "In the beginning, the early princes and princesses were raised to see each other as brother-husband and sister-wife, but King Vortigen's children had not. He hadn't been, nor had his wife. So the practice simply fell away."

"Huh." Anna chewed on her lip. "Papa had a sister, didn't he?"

"Yes. She was married before I was born, however, to a king who lives to the south. We've never met her."

Anna hmmmm'd. "Well. Good, er. Good to know," she said, blushing some more.

"Why?" Elsa asked, rather confused.

Anna's blush fluctuated through a range of pinks. "Oh, you know. It's just one of those things people say. Have you—ever thought about, um. Getting married? To, you know. People."

"No." When Anna just stared at her, clearly expecting more, Elsa shrugged. "I never expected to be able to. I thought. . . I would always have to hide."

"And—now?"

"I don't think I shall marry, no."

Anna looked almost distressed. "Why not?"

Elsa shrugged again. "I've simply not thought about it. Even when I wanted so badly not to be alone, I never thought of being married. Not once. Besides. . ." Still holding Anna's hand, she shook it gently. "I already have my heir."

Anna smiled, but as if her heart weren't truly in it.

"Do you want me to marry?" Elsa asked.

"No," Anna said quickly. "I—no. I just. . . don't want you to think you have to be alone forever because you'll. . . hurt someone."

So Elsa hadn't fooled her. Well, she hadn't lied, either.

"When we are asking the gods to grant our heart's desire," she said, "we ask for what we truly want. And all I ever asked for was you."

Anna stared at her, some incomprehensible emotion in her face.

Elsa extracted her hand from her sister's, feeling suddenly frail. "Let's put these away. You seem to have taken down half the library."

". . . Right," Anna said.

They filed the books away in silence; Elsa knew their places perfectly. She felt embarrassed to have said so much, and yet oddly distressed, as if she had also said too little.

But as they walked upstairs to their rooms, Anna stopped and hugged her tight.

"Good night," she said, almost fiercely. "Sweet dreams."

Then she kissed Elsa's cheek and darted away to her room.

Sweet dreams, Elsa thought, as the warmth of Anna's embrace and her kiss lingered like dusklight after sunset.

The sky was awake.

The snow was tinted green beneath the moving curtain in the sky and the stars glowed bright and cold in the dark spaces beyond. The snow was flat flat flat and looped from horizon to horizon, unbroken and empty.

Not empty.

The man had black hair and black brows flecked with snow. He was young and old at once, with a young man's strength and vigor and an old man's ancient eyes.

I have been waiting, he said without words.

Here, where the world is dead yet living, living yet dead.

You sit upon my throne, queen of my blood.

Your gifts are my gifts, living scion of my dead brother.

And I am coming.

Elsa awoke to a deafening crash.

She sat bolt upright in bed, her breath frosting the air with ragged gasps, and saw her bedroom floor littered with shards of crystallized glass, and the moon shining free and cold on the snowflakes in the air.

A/N: Man, I've been writing in Harry Potter fandom for so long that I feel really clumsy writing something different. Do let me know what you think of it; I love hearing from you lovely people :)