Elsa sat on her ice armchair, her gaze fixed on the moving and speaking sculptures that rose from the floor in front of her before sinking back to make room for more. But she had ceased to actually see them for some time.

She had become unerringly good at pulling memories out of ice. These days she barely needed to concentrate on the memory she wanted to see for it to appear in front of her. And they would repeat as often as she wanted them to. The wonder she felt about it had never quite faded away. It was like photographs, only with movement, sound, form, and displaying any single moment she could think of.

Above her, the ice wall flickered with the myriad of images, flat but still animated and voiced, and in full, glorious colours to boot. The wall was different – what appeared there seemed more like thoughts or echoes of what could have happened, or possibly manifestations of spirits or souls. Her mother sometimes showed up, still as beautiful as when she had last seen her, speaking directly to her. Anna had also appeared and talked to her a few times over the years – but she would usually look like the little girl who had relentlessly knocked on her door, and only once or twice like the brave young girl who had climbed the North Mountain to find her. This had always made Elsa a bit uncomfortable. Her mother was gone, but Anna was still alive and well. Elsa was sure of that – she checked every day, and the ice never lied.

She could conjure any memory she wanted there, of something that had happened ten seconds or a century ago, a mile away or at the other side of the world. She had spent countless days or weeks of her time browsing through them either at random, or in search of something specific. There were a lot she did not quite understand, of course, coming from a place and time so far removed from her own as to be utterly alien to her, and others she simply did not want to be spying on or even know about, but there were also so many she did understand, and from which she learned or simply got some entertainment. But her favourites were of course those of her family.

Elsa would spend days searching for the right instants to conjure, and then watch them endlessly until she knew by heart every movement, every word spoken, every flicker of a gaze or hesitation in speech. She would walk blissfully among scenes of unadulterated joy, of her child self playing with her sister in snow she had created, or her adult self teaching Anna to skate, or helping her niece taking her first steps…

And there were all the memories of which she was absent, but that she cherished just as much, if not more. Her little sister, looking regal and dignified in her formal dress, talking to ambassadors with a poise that would have made their parents proud. Anna and Kristoff having a picnic with their children. Her niece and nephew playing together. Gerda trying not to see the faces her brother was making while she strove to listen to her tutors. Elsa loved those scenes all the more that she could not even have witnessed some of them in the first place.

Of course, some memories were more bittersweet. She did not like them, but they tended to pop up from time to time when she let her mind wander. There was Anna knocking on her door, asking her to play or to let her comfort her after their parents were gone, or getting hit by her sister's powers, in the head or the heart… And there was one memory that Elsa knew was always around somewhere, the memory of the day she had knowingly betrayed a promise to her sister, and had pushed her away before going alone to Ahtohallan. Every time that Elsa stumbled on it, she could not help feeling bad no matter how many good reasons she found for her actions of that day. It was usually after times like this that an image of Anna would talk to her from the ice wall, and tell her that she understood, and that she had made the right decision. It seldom helped. On those days, Elsa would ride the Nokk back to the Northuldra village, to spend some time with people who were not made of moving ice. She would ask Gale to send a message to her sister, and consider visiting her. But soon the appeal of the memories brought her back to Ahtohallan.

Another memory rose from the floor in front of her. This one was quite old, and very familiar. Her mother was singing a nursery rhyme to Anna and herself about Ahtohallan. This was a scene she had often watched. But only now was she beginning to suspect she had failed to hear the actual warning in the nursery rhyme's lyrics.

Dive down deep into her sound, but not too far or you'll be drowned.

Years ago, Elsa had dived too far into Ahtohallan, and had nearly drowned – actually, she had, and was only alive thanks to her sister. And she had never doubted after this that she had faced the worst danger that Ahtohallan could present. But now she was realising that there is more than one way to drown.

She remembered her first years living among the Northuldra quite well, even without the need to conjure the corresponding memories. Living in the forest among her mother's people and the nature spirits, free to use her powers without fearing to harm anyone or be judged by anyone, had felt like a second birth. Anna, Olaf and Kristoff were only a Nokk's ride away – the water spirit could cross the distance faster than a tidal wave. And she was free to explore the memories in Ahtohallan whenever she wanted, and occasionally to speak with the image of her mother.

And then she had begun to look for closer memories in Ahtohallan. Memories of her last charade night with Anna. Memories of her talk with Honeymaren, on their way back from a hike to visit one of the sacred sites of the Northuldra, where some of Elsa's ancestors had been buried. Memories of Anna announcing to her that she was pregnant. Memories of herself holding her baby niece in her arms, with her sister at her side, tired but glowing with pride. Memories of watching Kristoff taking care of his daughter while Anna slept, his large fingers operating with infinite care, while Olaf was peppering her with questions that she could not easily answer.

And she had come back again and again to Ahtohallan to relieve these memories, keeping them fresh forever in her mind and in the icy walls of the magical island. And she enjoyed them so much that she had not even noticed when she had ceased to appear in them…

From her fortress in Ahtohallan, Elsa could watch her sister's life minute by minute, except, of course, the moments that belonged only to her and Kristoff. She could watch her niece and nephew growing up into fine, healthy young children. Rewatch any event that Anna had described in her latest letter. Relive at will their best memories together. And, without realising it, she had slowly ceased to form new memories with them. Her family and friends had become white images that she could watch again and again, perfect moments forever preserved in ice. She had never felt that she was drifting away from them – how could she have been, when she would never spend a day without seeing them?

Maybe she would have noticed that something was amiss if there had been one dissonant note among all this. But every memory she picked up from Anna and her family showed them perfectly happy – just as she herself was, living among them every day like a shadow. She would laugh with them, smile when they talked about her, listen to the stories Anna would tell her children – without ever realising that she was with their memories but not in them. Only now did she begin to understand that some memories of her friend Honeymaren standing alone on a beach looking in the distance may not have been as happy as she had thought.

Discovering Kai on the beach had come as a shock. Of course, part of it was that she had not been expecting to see anyone there, let alone her nephew. She had been enjoying a ride around Ahtohallan – one of her few regular activities that did not involve the ice memories, which she did as much for exercise as for the breathtaking views – and part of her enjoyment was that she could be alone for some time, without even the memories to disturb the peace around her. That day, she realised now, the Nokk had been particularly difficult to control and had directed her toward this lonely beach despite her best efforts. Elsa liked riding on beaches sometimes – the Northuldra did not come very often to the shore, which meant that she could play with her powers in a different environment without fear of hurting anyone. And she had been very surprised to hear a distant cry, and all the more that the voice had seemed familiar…

But that had not been the real shock. Elsa had recognised her nephew instantly, of course. She had watched him only the day before, although slightly younger, enjoying his latest birthday and playing with his sister. But she had been astounded at how… lively Kai had seemed. She had come to consider the ice memories as just as accurate as real life. Now after seeing her flesh and blood nephew in front of her she had realised they were not much more than glorified photographs.

She very rarely brought anyone to Ahtohallan, mainly because few ever asked, as if everyone who knew her enough understood implicitly that this was her secret garden. She had taken Anna there a few times, to show her more memories of their parents, but that had been a long time ago. Yet, for some reason she had not really been able to explain at the moment, bringing Kai there had seemed the only possible choice. She could of course have brought him to the Northuldra, where she was sure they would have taken good care of him, while she would have sent a message to her sister. But, faced with her crying nephew on this lonely beach, her only thought had been to bring him with her to the safest place she knew. It was only after she had laid him on the most comfortable ice bed she could conjure, draped in one of the few Northuldra scarves she had brought to Ahtohallan, under a lens of ice that would keep him warm by concentrating the heat of the sun – such as there was to be seen behind the clouds – that she had tried to find reasons for her decisions.

She had thought that maybe she had wanted to keep the boy as close to her and as safe as possible, just like she had felt when Anna had given her baby Gerda to carry for the first time. Then she had reasoned that she had probably wanted to make sure that Anna was all right as soon as possible, and to learn where her sister was. Elsa did sometimes check on her sister almost in real time, but had not done so in the last couple of days, and there was the possibility that Anna had planned a surprise visit of which Kai would have been the advance guard, although that would not explain how he had would have ended up alone on this beach.

But now she suspected that the real reason was that she had wanted to be able to see Kai next to an ice memory, just to let it really sink in how one was only a pale, lifeless copy of the other.

And now, seated on her ice chair and looking at the memories folding and unfolding in front of her, replaying the events of the previous day, Elsa felt a sadness, tinted with shame, that she had not experienced in a long time. Although she now had seen more than enough to know the whole story behind her nephew's presence here, she could not stop replaying a set of memories over and over again, feeling more wretched every time.

"Did I stop caring for Elsa?" the ice Anna in front of her was saying, ambling in a part of the gallery that has risen from the ice. "Why did I let us drift away like that? Is it because of the kingdom? The children? Or is it because Elsa wanted it that way?"

The ice Anna sank into the floor, replaced by Anna and Kristoff on a carriage bench.

"If she did want to stay on her own…" the ice Anna said, "then I should have tracked her down to make her remember she swore never to close the doors between us again. I should have tried to understand what could have caused her to do this. Maybe it's something I did, or said, or did not do or did not say, or did at the wrong time, and I never made sure of that!"

The animated statues disappeared, merging as they did into statues of Anna and Gerda.

"Why don't we see Aunt Elsa any more?" her ice niece asked.

Elsa started as she heard a faint voice behind her, almost echoing her niece's image. She raised from her armchair and moved back quickly through the larger room toward the alcove where she had left Kai. But she did not have a long way to go before she found her nephew, standing in front of an ice sculpture of his sister on her horse searching him through the woods. Elsa had seen that one earlier, when she had been piecing the events of the previous day, and had marvelled at her niece's courage almost as much as she had shuddered at her foolishness. If she had needed any proof that she was Anna's daughter, she would not have needed another one.

Kai had seemed to sleep so soundly when she had arrived in Ahtohallan that she had not thought twice of leaving his side for a moment – but here he was, visibly fully awake among the statues. It seemed the sleeping habits of seven-year-olds were another thing the ice memories failed to convey correctly. Elsa slowly walked to her nephew and crouched to embrace the boy, who started for a second, before sagging into her arms.

"Mama?"

"Hello, Kai," Elsa said gently. "I'm your aunt Elsa."

The boy tensed as he turned around to face her. Elsa let go of him and stood up. He considered her gravely.

"You don't look like the portraits I have seen of my aunt," he said quizzically.

"I was a bit… younger on those portraits," Elsa said.

"Your hair is different," Kai said, still studying her gravely.

Elsa smiled as she tried to gather her long hair and pull them behind her head, in something vaguely resembling the braid she once sported. Kai's eyes lit up.

"You do look like her," he said. "Sorry for saying you did not."

"That's OK, Kai," Elsa said, crouching down again to be on his level. "I'm sorry. I have not visited you for far too long. It's my fault."

"Weren't you at one of my birthdays? When I was little. Gerda said you were."

"Yes, your third birthday. And now you're all grown up," Elsa said. "I'm really sorry, Kai, I should have come for all your other birthdays. They looked great."

"Yes, they were! Er… how do you know that? Did Mama tell you?"

"No, I watched them here."

"How did you? Did Mama send you the photographs?"

"No, the ice showed me."

"The ice statues showed you my birthdays?"

"Do you want to see them again?" Elsa asked, beckoning to him.

It took her a few seconds after taking his hand to realise that it was cold. She remembered that another reason for which she seldom brought people to Ahtohallan was the freezing cold, which had managed to bother even her once.

"Aren't you cold, Kai?"

"Yes, a little, Aunt Elsa."

"Let's go to where it's warmer, OK?"

She gently led her nephew toward a part of the room where the ceiling was made of ice instead of rock. She waved her hand. The ice above them twisted and changed, forming into a lens. A warm glow surrounded them.

"Better?"

"Yes, thank you, aunt Elsa," Kai said. "Er… what is this place?" he asked after some hesitation.

"This is Ahtohallan, the river of memories."

"Oh, like in the nursery rhyme Mama sang sometimes to us?"

"Yes," Elsa said, stopping short of saying that she had sung it with her. She was shocked to realise that she had really considered her singing in unison with an ice memory of her sister the same thing as singing with Anna. She bent and grabbed Kai in her arms, holding him tight.

"I am sorry, Kai. I left you, and your sister, and your mother. I spent so much time with their memories that I did not spend any time with the real yous," she whispered.

"The ice statues are memories?"

"Yes. Look," Elsa said, sitting on an ice chair that rose from the floor at her command, and taking Kai on her lap.

The memories emerged from the ice, moving around for a few seconds, speaking a sentence or two before fading into the floor to leave room for another one. Kai laughed and clapped his hands as he saw an ice memory of himself dancing and playing. Elsa realised that the sound of his laughter felt nothing like that of his ice counterparts that she had spent so many times watching. It did sound exactly the same, but listening to it while holding her flesh and blood nephew on her lap touched her heart in a way no ice memories had. Elsa fleetingly wondered how it would feel to see her real sister again and realised she could not wait for it to happen.

It took her a few seconds to realise that her nephew had stopped laughing and was beginning to cry. Elsa hugged him tightly while checking the memory in front of them – sometimes when she let her mind wander the memories were not quite the ones she wanted to see. But that one showed him playing with his sister, under the loving gaze of their parents.

"What's wrong, Kai?" she asked gently.

"I… I shouted at Gerda," Kai said between two sobs. "I was mean to her. I ran away from Mama and Papa. And Sven is going to… leave," he wailed.

Elsa hugged him tighter.

"They are coming to find you," she said as soothingly as she could. "Look," she added, waving a hand.

A carriage formed out of the ice, with Kristoff at the reins and Anna dozing adorably against him. She jerked awake and looked around her.

"Are we there?" the ice memory of Anna asked.

"Soon," the ice Kristoff said, stifling a yawn. "Go back to sleep, I'll wake you when we are here."

"I was not sleeping, I was resting my eyes! How's Sven?" the ice Anna said, looking at the carriage behind them.

"He has managed to fall asleep," came Olaf's voice from behind. "The doctor had said that was good for him."

"That was not long ago," Elsa said, hurriedly dismissing the memory. "They should arrive at the Northuldra village soon. We will go and meet there."

"But where was Gerda? I did not see her!"

Elsa waved a hand. Another memory formed out of the ice, but it represented Honeymaren riding on a reindeer, holding the bridle of a horse who walked at their side.

"That's Gerda's horse! But where is she? Who is this woman?"

"A friend," Elsa said, concentrating. The ice twisted and reformed into an image of Gerda, clutching at the sides of a small boat that seemed to be moving quite fast across the water.

"It's Gerda! Why is she on a boat?" Kai said, jumping from Elsa's lap to run to the ice statue.

Elsa was looking at the frozen whirls of water around the ice boat, and at some ice leaves fluttering around Gerda. She had had only suspicions until now on how Kai and Gerda had managed to reach the Enchanted Forest so quickly – it was not always easy to see in an ice memory that a cavern was moving. But now she was sure. And she also had a good idea of where Gerda was headed to.

"Come," she said, standing up and taking Kai's hand again. "I will show you."

She led him across the ice corridors of Ahtohallan as quickly as she could, as she did not want her nephew to have the time to get cold after leaving the warmth under the lens. A few minutes later they emerged on the frozen beach that circled the island. Kai, who had been gasping with awe at each step, let out another appreciative "Oooh" at the sight of the sea spreading in front of them. Elsa scanned the horizon, and soon saw what she was looking for. A dot was growing bigger, and soon resolved into a small boat with a little girl inside.

Elsa gently led her nephew toward the point where the boat would touch ground. He actually failed to notice it, as he was looking behind him at the majestic sight of Ahtohallan rising above them, and only turned toward the sea as the boat gently washed ashore. Its occupant had seen them, and disembarked on shaky legs as soon as the boat stopped.

"Gerda!" Kai shouted, letting go of her hand and running toward his sister.

"Kai!" his sister shouted back.

Elsa watched the two siblings run across the beach to jump into each other's arms. The spectacle once again moved her in a way no ice memory had ever managed to do in the past years. It evoked other memories in her mind, of two sisters running into each other's arms. She had watched these memories many times over the years, as lively as on the day she had experienced them. But today, the simple recollection of them brought tears into her eyes.

She slowly made her way across the beach toward the two siblings who were hugging each other, half crying, half laughing, and talking excitedly at the same time. As she got close, she felt the same shock at seeing her niece in the flesh as she had when seeing her nephew. The memory of holding her as a baby in her arms rose in her mind. It felt nothing like anything she had felt while watching the scene re-enacted in ice.

She stopped a dozen feet away from them and looked at them silently. She knew she would be able to rewatch this scene as often as she wanted, but now she had realised that it would never quite be like what she was watching right now. She drank in the sight of Anna's children, trying not to think of the many moments like this one that she had only witnessed as lifeless ice statues.

Eventually the children broke their embrace to face her. Gerda looked at her and curtsied.

"Good morning, Aunt Elsa," she said quite politely. "It is a pleasure to see you again."

Elsa crossed in an instant the distance separating them and grabbed both of them in a hug. To her immense joy, they returned it readily. This was another thing ice memories never did. Elsa was the first to admit she was not a people person, but she had not realised how much she had missed the warm embrace of a loved relative. The hug went on for a long time. Eventually Elsa drew back, and looked at the children. She had not missed a day from their lives, and had in fact watched a lot of them multiple times over, yet she felt as if she was seeing them for the first time in years, as if the ice memories had never counted.

"I'm sorry," she said eventually. "I should have come to see you more often."

"We should have come to visit you, Aunt Elsa," Gerda said gravely. "I think… I think Mama, I mean, Mother, forgot it too."

Elsa straightened up.

"But you did not," she said to her niece.

"I loved all the magic things you did," Gerda said in a small voice, as if she was being scolded. "I mean… you really did them, right?"

"She showed me some magic!" Kai said excitedly. "There are statues of ice who move and talk!"

"Is this Ahtohallan?" Gerda asked, slowly enunciating the unfamiliar name. "The river of memories?"

"Yes. Where every memory can be found. And where you can lose yourself among them," Elsa said.

"Can we go back to show Gerda the magic statues, Aunt Elsa?" Kai asked excitedly.

"Oh, I don't want to bother Aunt Elsa," Gerda said, very unconvincingly.

Elsa laughed.

"I can show them here. Memories are all over Ahtohallan. They are simply easier to show inside, but I can bring them out here as well."

She waved a hand, then moved between the children, taking each by a hand, so that all three of them faced the awe-inspiring bulk of Ahtohallan. Ice rose from the frozen shore, and formed into memories. There were the children playing together, and with their parents, and even with Elsa, when they were much younger. Gerda and Kai reacted with awed exclamations and laughter.

"That was awesome, Aunt Elsa!" Gerda said as the last memory slowly sank back into the ground. "It was even better than I remembered!"

"I got a bit better at it," Elsa said. "Maybe too much."

"Why do you say that, Aunt Elsa?" Gerda asked.

Elsa turned to look at her niece. The girl returned her gaze with the serious eyes of someone who had made her first steps toward adolescence. This was not something she had ever been able to catch on in any of the ice memories of her niece.

"I spent all my time there, Gerda. Watching memories of you all. That was not good."

"But… these memories are awesome!" Gerda said, with a gesture toward the ice in front of them. "If I could watch any memory I liked… I would do that all the time!"

"Yes," Elsa said, "that's what I did. These memories are wonderful indeed. But… they should not replace the real thing. I spent so much time looking at them that I forgot to actually spend time with you. With the real you, I mean."

Gerda wrinkled her face in an obvious display of concentration.

"OK," she said at last in a half convinced tone. "So, will we see you more often now?"

"Oh, please say yes, please say yes!" Kai said from the other side.

"I promise."

Both children let go of her hand to clap and shout cries of delight, although Gerda stopped midway and began a curtsy.

"Thank you, Aunt Elsa," she said. "It will be a pleasure."

Elsa laughed, and Gerda could not retain a giggle in return. They all hugged once again.

"Aunt Elsa," Gerda said at last, "could you warn Mam… Moth… our parents that we are safe? I would not want them to worry."

"They will be mad at us," Kai said. "It's all my fault. I ran away from the castle."

"No, it's my fault," Gerda said. "I should not have shouted at you, and I should not have gone out of the castle alone after you."

"Actually," Elsa said, "I think that neither of you would have gotten very far without a little help from my friends. Isn't it so?" she asked the air around her.

A gust of wind blew, bringing some dead leaves that whirled toward the ground in a decreasing spiral, as if trying to make themselves smaller. There was a splash of water behind them. They turned to discover water rising above the waves in the shape of a horse. It lowered his head.

"I know what all four of you did," Elsa said softly, while Gerda and Kai gasped at the sight of the water horse. "Thank you. And sorry. It will not happen again. I swear."

"Is that the horse you rode when you brought me here?" Kai asked. "I thought we had been riding on water."

"Yes. He's the Nokk. He also brought Gerda here. And he will take all three of us back to the Northuldra."

"Er…. Aunt Elsa… I really would like to warn Mama and Papa, er, Mother and Father, that we are safe, even if they are angry after us. Is there a way to, er, ask the wind spirit to do it? Or could the Nokk bring us directly to Arendelle?"

Elsa smiled and waved a hand. A large scene erupted from the ice around them. A whole village formed, with tents and people coming out of them. Gerda noticed Honeymaren, and her own horse grazing alongside some reindeer. In the middle of it all a carriage moved slowly, with Kristoff at the reins and Anna at his side.

"This happened some time earlier at the Northuldra village," Elsa said. "Your parents followed you there. It took them the whole night since there were no earth spirits to carry them, but here they are."

"They brought Sven!" Kai said excitedly. "He's still with us! Can we go see him? Please?"

Elsa smiled, and walked to the Nokk, turning it into ice with a touch. The horse ran across the beach, its ice hooves clattering on the frozen ground. Then he walked up to them, and waited patiently while Elsa climbed and hauled up the children with her.

"Is he strong enough to carry all three of us?" Gerda asked. "I could go back with the boat," she added, in the half-hearted tone of someone who is dearly hoping their suggestion will not be accepted.

"The Nokk can be as strong as he's needed to be, just like water," Elsa said. "Now… let's go."

The horse ran across the beach and onto the water without breaking its pace. The sea was much calmer now. The children cried in surprise, then giggled in delight as the Nokk ran across the small waves as easily as if they had been molehills on a grassy plain.

Elsa had done this ride countless times, and never failed to enjoy it, although she liked it better when she was riding toward Ahtohallan. But she had never enjoyed it as much as today, with her niece and nephew sitting in front of her on the Nokk and commenting excitedly on everything they saw, even if it was only some foam on a wave crest. Nor did the ride feel so short. It seemed to Elsa that she had barely begun to savour listening to Gerda and Kai's awed cries that the shore of the mainland appeared in the distance. She knew this was a special moment. The Nokk, like the other spirits, was not at her service like a pet horse kept in a stable. It was the embodiment of a powerful force of nature that only allowed her to use it because it had deemed her worthy of it. Today this situation had happened partly because of its will, and there was no argument about its cooperation in bringing back the children home. But it may not be ready to give them a ride whenever they asked for it in the future. She would have to enjoy this moment now, with the consolation that she would be able to evoke pale echoes of it later on as ice memories.

Dead leaves danced around them amidst sprays of foam that shot up like fireworks.

Author's Notes: Apparently, some of the Frozen novels establish that only Elsa can come to Ahtohallan or ride the Nokk. Well, I have not read them yet, and novels are only canon as long as the next movie does not contradict them anyway, so I will conveniently ignore that.

I may also have extended Elsa's powers a bit from how they appear in the movie, but her powers are canonically growing with age and she's now a woman, so I don't think it's a stretch to have Ahtohallan be the ultimate knowledge base.

At least until Frozen 3 comes out and contradicts all of this.