Disclaimer: I own neither Rise of the Guardians nor Frozen. Pity.

A/N: So this is entirely because of an awesome picture that Kazeki posted on deviantART, "The Cold Never Bothered Me Anyway", which has Elsa and Jack, and I was like BEST CROSSOVER/PAIRING EVERRRRR. And then this story resulted! Who knew there was already an established ship for them, but hey, I'll gladly add to it! Read, enjoy, and please review!

to thaw a heart

i.

He was…cold.

Not because of his powers, not because of the way frost sparkled and spiraled from his frozen shepherd's staff or the way he could dance through the air, as light and transparent as a snowflake. He was accustomed to the cutting bite of arctic gales, but, to tell the truth, he wasn't certain if he'd ever felt them to begin with. He'd see the humans cringing and hunching into themselves, and he would stand there, bare-footed and straight-backed, and wonder at their pain.

Did the kiss of snow hurt? He'd always enjoyed it…or at least, he'd always enjoyed it for as long as he could remember.

And that ultimately was the problem.

There was something missing inside of him, something empty and aching and lost, and he was convinced that, sooner or later, if this ignored existence continued…then his own frost would curl into that space and fill it with ice and it would never, ever thaw.

But Jack didn't know how to solve this dilemma—the children always failed to notice him, even when adults referenced his presence, so tongue-in-cheek—and he disappeared into the whirling blizzard, wishing he could be a figment of the imagination.

ii.

Riding the back of a northern wind, Jack skimmed the tops of the light, sparing clouds and shook his head. What kind of autumn was this? These clouds would never produce the kind of snow he wanted, so, once again, it seemed that it was up to him to bring winter.

He dove out of the sky, an icicle cut free from the fringe of the heavens, and descended upon the earth. He vaguely recognized the coastline and the mountains as ones he'd seen before—Arendelle, he dimly recalled, was this kingdom's name—and with perfect grace, he lit upon a windowsill, one of the castle's. He favored this perch, as it allowed him to see the whole of the village and the harbor, but before he could bring his power to bear, something smacked into the window behind him.

Nearly jumping out of his skin and certainly jumping off the sill, Jack spun around in mid-air, his staff brandished defensively.

And, to his astonishment, he saw snow plastered on the inside of the glass.

"Man in the Moon," he breathed, and he floated closer and cautiously set a foot back on the sill. "What just happened?"

He outstretched a pale finger, tracing the snow's exploded debris, and peered through the glass, but what he beheld only served to further bewilder him. The entire interior of the castle hall was a winter wonderland! Huge drifts caused deep ravines and towering ridges, and icicles decorated the sharply sloped ceiling like the inside of some glacial cavern. The tinkling sound of children's laughter reached his ears, and he eased through the glass, as insubstantial as a ghost, and marveled at the sight.

"Again, Elsa, again!" a tiny, red-haired girl giggled, stamping her feet down in the fresh white powder.

"I didn't mean to hit the window," another girl replied with an air of self-recrimination. This one was slightly taller and sporting white-blond braids.

Jack's lips parted as he raced to assemble this puzzle. Was that child responsible for the snow? Did she have the same kind of powers as he did, and if she did, then maybe there were more people like them, and maybe—

"Aw, c'mon, Elsa!" the redhead protested, looking grumpy as she crossed her small arms on her chest.

Elsa sighed. "Okay, okay," she capitulated, and she looked up at the gigantic icicle dangling in front of the window—the actual target.

Jack startled for a second; she was looking directly at him! But then he realized, when she expressed no surprise at his presence, that it was only because he hovered behind the icicle; she wasn't looking at him at all.

She couldn't see him.

He retreated to the sill, though he remained within the hall, and observed with dulled interest.

"Knock it down already!" the smaller girl urged.

"I will, Anna!" Elsa assured her with a somewhat exasperated glance and a fond smile. "Just you watch!"

Jack certainly watched as crystalline lights flashed along the blond's small fingers in little sparks like sunlight refracting off snow, and then, suddenly, frozen flakes were called into existence and spiraled sharply until they achieved their desired form: a perfect sphere.

"Here goes!" Elsa declared, and she drew her arm back, as if she were about to throw it the conventional way, but then more magic flared along her hand.

Jack ducked back instinctively, although an awed grin stretched his lips, as the snowball struck the icicle with tremendous force; the fragile cone splintered at the impact point, and the shattering pieces plummeted to the soft powder far below.

Anna danced about, clapping loudly and cheering her sister. "Woo! You got it, Elsa! Yeah!"

Elsa tucked a stray lock of hair behind her ear, pleased by this success and its recognition, and she smiled shyly. "Do you want to build a snowman, Anna?"

She shook her head, red braids swinging, and pointed at the tallest of the snow-hills. "Nope! Wanna go sledding! Make me an ice-sled, Elsa!"

"You better start running, then!" the older girl laughed, and as the younger took off at a headlong sprint, she conjured a perfect toboggan in Anna's path. Anna threw herself upon the sled with much exuberance, and Elsa ushered it into motion, compelling the snow beneath it to undulate like ocean waves, and it carried the little girl up to the crest of the high hill.

It was just then that the king and queen opened the hall's great doors, and they rushed into the knee-deep drifts.

"Elsa! What have we told you about making snow inside?" her father remonstrated.

Elsa frowned. "You said people would see if I did it outside, Papa," she replied, using simple child's logic.

The king sighed and ran a hand back through his hair. "We'll have to tell the servants so they can shovel this place out," he remarked.

"Aw, do they have to?" Anna complained from her lofty perch. "It's so much fun!"

The queen trudged over to the bottom of the hill, holding out her arms invitingly. "C'mon down from there, sweetheart. It could be dangerous."

Elsa stiffened. "I would never let her get hurt!" she protested, and little ice particles materialized around her fists.

Jack frowned, feeling as if he were trespassing, and he melted back through the window, leaving only curling vines of frost behind. Once outside and soaring into the sky, he decided not to bring winter early to Arendelle. That little girl would only be blamed for his antics, and he did not wish such a thing to happen.

He did, however, make a mental note to come back; perhaps this Elsa still did have the answers he sought, and even if she didn't…maybe somehow, he would get her to notice him.

iii.

She was…frozen.

Not from the snow that unfurled from her fingertips as if she were some archaic weather goddess; her snow, and any snow, had never caused her even the slightest chill. When her sister bundled up in layers of fur, or her parents huddled in front of a roaring fire—until, she remembered, the day when no fire would ever make their skin warm again—she would always watch in slight puzzlement, and from her observations, she cobbled together a definition of cold.

But their cold was not like her cold. Her cold paralyzed her, for her cold was fear, and it went deeper than the skin, deeper than the blood, deeper even than the bones. It haunted her at night with terrible visions of frigid waters rising up and swallowing her whole, and it dogged her steps during the day, whispering that if she melted even the slightest bit, it would unleash its terrible powers and cause havoc and mayhem.

Or worse, it would hurt Anna again.

Elsa closed her hands into fists and squeezed and squeezed and squeezed until the supple suede of her gloves creaked in protest.

That would never happen again.

iv.

Lonely years passed, and the only comfort Elsa found was in drawing frost patterns on the windows because, somehow, other designs would appear beside hers. She never knew how this miracle manifested, but she didn't dare to question it—she had lost everything else, and this small comfort would not be counted amongst them.

She painted ice on the inside of her bedroom windows, and Jack Frost answered with his own doodles on the outside.

He had resigned himself to being unseen to this girl, but interacting with her, even in this unconventional way, was almost enough to make him happy. She had a tendency to draw graceful clipper ships surrounded by towering waves, and he could sense her preoccupied sorrow in those sketches, so he would always carry the ship to safety, making it ride out the swells and guiding it to safe harbor.

At first, he understood that she painted thusly out of some sort of grieving, but then, as time wore on and he reliably returned the ship to her, he realized it had become something else—that she wanted to see the ship come home, that she clung to the hope in his art even when reality was as crushingly heavy as the waves.

But, one day, she stopped drawing altogether.

Jack tried to coax her back, daring to begin the frosted designs himself, but Elsa was more introverted than ever, and the sight of ice only seemed to upset her. She would open the windows and wipe and scrub with her gloved hands until his frost was gone.

"They're dead, they're dead," she sobbed, "and they're never coming back! Stop taunting me!"

"Please," he begged, arms spread imploringly, "I just want to help you!"

But she could not hear him, and her grief and twisted guilt consumed her.

Frustrated and wounded and so sick of being invisible, Jack abandoned Arendelle and vowed never to return, flying off into the dark reaches of the snow-covered mountains and dashing the tears from his cheeks.

v.

But never is a long time, and Jack wandered back, somewhat against his will, some while later.

He had heard tales of an unexpected blizzard covering the kingdom in the height of summer, and curiosity had compelled him to return—curiosity alone, he sternly told himself, not any sort of concern. By the time he arrived, though, the mysterious snows had vanished, and Arendelle basked under a summer sun again.

Frowning and careful of not touching anything with his staff, Jack landed on a once-familiar windowsill; the window itself was open, which had never been the case before, and he stood on the ledge and watched a girl who certainly looked like Elsa—but also, he thought, looked nothing like Elsa—laugh and say some parting remark to Anna before she stepped inside her bedroom and shut the door all the way.

Still wearing half a smile, the beautiful young queen turned about and only made it a few steps before she stopped dead.

Jack realized distantly that she was staring directly at him, and he wondered if that were why his heart felt tight in his chest…

She blinked several times, as if doubting the information of her eyes, and then lifted her hands defensively; ice crackled at her fingertips. "Who are you, and how did you get up here?" she demanded, the twinkle of mirth fading from her eyes to be replaced with grim determination.

He balked and nearly fell off the sill. "You can see me?" he blurted, shock cracking his voice.

Her eyes narrowed further. "Why wouldn't I be able to see you?" she countered.

Recovering somewhat, Jack waved his arms. "Because you never have before, that's why!"

Her stance relaxed slightly, but probably because she was confused, not because she trusted him in any way. "How could I have seen you before?" she pressed. "We've never met, and regardless, I've hardly left this castle in years."

"I know that," he said earnestly, and he grabbed onto the window pane and looked briefly back at her. "And we have met before, although you didn't realize it at the time. Remember this?"

With his forefinger on the glass, he traced out a clipper ship, and with an exhaled breath, he caused it to sail across a frosty sea.

When he turned to face her again, her jaw was sagging open, and her whole form seemed about to buckle; she somehow managed to remain standing.

"That was you?" she gasped. "But…you…you were never there before…"

He sat down on the sill, staff balanced against his shoulder, and shrugged. "I've always been there, Elsa. You just couldn't see me. It's alright—nobody can. I'm just glad you've finally figured out the secret…whatever that is."

She tentatively approached, and he found himself glancing aside; something about the way she walked was just…distracting. She laid a delicate hand on the frost patterns, as if they were something sacred, and without looking away from them, spoke. "How did you come to have ice magic?"

He scratched the back of his neck, ruffling his blue-tinted white hair. "Mm, well, that I don't know. I just woke up one day like this, empowered by the Man in the Moon. I…don't know why I have it, either. I just do."

"I was born this way," she whispered, still reverentially tracing the designs, and her brow furrowed in contemplation. "I was always so scared of it—my power, that is. But recently, I finally understood that in fearing it, I gave it strength; I gave it power over me. I had to embrace it as part of my identity and being, and then…well, then it's like now, I suppose." She glanced at him sidelong. "I wonder if that's why I can see you," she murmured. "Because I'm more open to everything now, including the possibility of you."

He smiled halfway, a crooked sliver. "Hey, it sounds likely enough to me."

She returned the smile, a small and close-lipped thing, and she tilted her head to one side. "So do you have a name, or should I just call you Ice Spirit?"

He chuckled at that. "Ice Spirit? Accurate, I suppose, but doesn't really trip off the tongue. No, the name's Jack Frost."

She extended a hand, her smile broadening. "Jack, eh? I'm Elsa."

He accepted the offer, and a spiderweb of ice crawled along their hands as they clasped. "It's nice to meet you," he replied honestly.

Their hands lingered for a moment, as if neither of them was inclined to pull away. When they did finally separate, the tiny threads of ice splintered and tinkled to the ground. Elsa studied her palm, caressing it with her other hand's fingers, as if she were trying to figure out a complicated puzzle. At length, she raised her eyes back to his.

"Was that…warm?" she asked.

He nodded. "Oddly, yes."

She frowned and extended her hand towards him again. He laced his fingers through hers, pressing their palms together, and while little sparkling snowflakes burst into evanescent existence, they felt no sting of cold, only the flush of heat.

Elsa tentatively tightened the hold. She didn't know what this experience was, but his skin was smooth and his grip was strong, and somehow, for being dusted with snow, he truly was warm…

Her thoughts were shattered as the door banged open and Anna barged in with her usual decorum.

"Hey, Elsa, it's almost time for supper," she declared cheerily, and then she giggled at the sight of her sister standing beside an open window with her arm extended. "Admiring the view, are we, sis? Haven't you seen it enough? C'mon, let's get going."

Elsa glanced at Jack, who shrugged disarmingly and slipped his fingers from hers.

"What are you waiting for?" Anna demanded, and she marched over and grabbed the queen's shoulders, propelling the older girl along. "You know we can't eat until you're present, and Kristoff is sta-har-ving! Off we go!"

Elsa didn't struggle too much, but she did keep staring back at Jack, a silent plea.

He nodded and grinned. "I'll be here when you get back."

A smile flitted across her face, and then she was gone, dragged along by the relentless Anna.

Jack settled more comfortably on the sill and studied his own hand.

It was still warm.

vi.

As days passed, Elsa found herself growing increasingly more anxious for Jack's arrival, and the rush of excitement when he did appear was enough to make her dizzy. They talked for hours as they drew icy patterns on the floor and across the walls and discovered that they had both experienced terrible isolation and found all the more comfort in each other's presence because of it.

He was charming and so easy-going, quick to both laugh and smile, and she found herself laughing and smiling all the more, found her heart growing lighter and easier with each second they spent together.

And she was sympathetic and attentive, and he could speak about the difficult times with her, could share his fears and his insecurities, and he had never before felt so visible. He could talk to her; he could touch her. In all the world, she was the only one who even knew he was real, and that was enough for him to feel real, to feel as if he belonged.

He found her one day, twirling awkwardly in the ballroom.

"Elsa, what are you doing? Trying to trip yourself?" he teased as he drifted in through the open window.

"Jack!" she exclaimed, and, inelegantly, she did trip, but she did not fall; he caught her, an arm about her waist, the other hand supporting her head. "Oh," she said, quietly, and she felt her cheeks heating as she gazed up into his eyes.

He, too, flushed, and with a clearing of his throat, he set her back on her feet. "You can walk well enough, from what I've seen," he remarked distractedly. "What were you trying to do, anyway?"

She huffed a sigh. "Dance," she grumbled in unenthused response. "Anna's wedding to Kristoff is only a week away, and I still cannot get the hang of this! Your feet are supposed to end up in the strangest of places."

Jack looked critically at the ballroom's floor. "I can see your trouble. This floor is much too rough."

She arched a brow in return. "This is the smoothest, most waxed wood in the castle. Which, admittedly, could be part of the problem," she added to herself.

He grinned and leaned his staff against the wall. "Wood is always rough compared to ice," he replied. "Shall we?"

Elsa appeared hesitant for a moment, and then she nodded. Within the space of a clouded breath, the entire room had been transformed into an ice palace; the floor sparkled and reflected the chandeliers above, and Jack glided gracefully to her side, his feet as bare as ever—it wasn't as if either of them needed skates.

"And shall we?" he prompted, and if she'd been able to focus more, she would've heard the slight waver in his voice. But as it were, her heart was beating too loudly in her ears, and she was just aware of accepting his hand and being drawn into his side.

"Try not to think about it too much," he whispered, his breath ghosting across her ear and sending, for the first time, shivers down her spine. "Just let it flow, like the magic. Moving should be easy…"

And he spun her about and sent her sliding across the floor, only to follow her at even greater speeds and catch onto her again. They cut arcs and spirals on the ice, weaving back and forth and leaving ribbon-like trails behind, and through it all, he was there to help her, a hand putting pressure just so on her waist, a steady and reassuring presence.

Suddenly, it was over, and she was trying to catch her breath as she found herself, once again, encased in the circle of his arms. He was gazing down at her, his eyes as beautiful and blue as their ice, and she couldn't stop her hand from acting on its own accord—it lifted and traced his cheek, slipping across the line of his jaw.

"Elsa…" he whispered, his breath misting.

She tore her eyes away from watching her fingertips leaving frost on his skin. "Yes, Jack?" she asked, barely audible.

He swallowed, and she felt his hands tighten on her, a nervous spasm. "I…I don't know how this is going to work," he managed to say. "You're human, and I'm…some sort of spirit…"

She smiled, the faintest of curves. "It's worth a try, isn't it?"

His gaze was so intense now that it was a wonder it hadn't bored all the way down to her soul and etched it with his ice. Slowly, he leaned in, and their breath crystallized on each other's lips for a last moment before he closed that distance and kissed her. Feelings she'd never dared to imagine rushed through her like winter's first sharp frost, prickling all her nerves and leaving her without a thought in her head except that she never, ever wanted to stop.

He must have felt the same, because he kissed her again and again with a growing urgency, as if he were convinced this was his one chance to have her and he would not be deprived of that.

It was only when they felt the steam rising around them that they pulled away and became aware of their surroundings: all the ice that had coated the ballroom had sublimated, turning abruptly into water vapor and filling the air with its fog.

Elsa laughed as she swayed into his chest, able to hear the reverberating rumbles of his answering chuckles.

"Well, love is the only way to melt my ice," she remarked after a while, once their amusement had quieted and the fog had settled.

Jack rested his chin on her hair and pulled her a little closer. She was here, and he could feel her and she could see him, and that was all that mattered: he wasn't invisible any longer.

Smiling, he confirmed simply, "It looks like it thawed both our hearts."

vii.

They were warm.

It wasn't the same as ordinary warmth, like the flickering heat of a fire or the steady blaze of the sun. It was internal and contradicting, surrounded by ice but sustaining that ice, and it meant that, for a while, neither of them had to stand in the darkness and wonder; neither of them had to be alone.

And they wouldn't be.

fin.