Blame the fact I found "Dark" Jack Frost pics while trolling through the net. I fully place the creation of this plot bunny on those.
We all know the story of the Guardians. North, guardian of wonder and innocence. Tooth, guardian of childhood memories. Bunnimund, guardian of hope. Sandman, guardian of dreams.
However there are always counters to such forces. For example, North's evil twin, Krampus. Where North leaves toys and small candies to the children of the world, Krampus takes from them. Where North is jolly and good natured, Krampus is cruel and vindictive when good cheer North brings has been lost to the children.
North doesn't like talking about his dark side very much.
Indeed, all spirits have a dark side to them. Most of the time said aspects never meet their evil half. And the Man in the Moon uses his light to shield said evil from Pitch Black.
To be fair, most of these evil twins consider Pitch to be a total poser.
However sometimes Evil is subjective. And two halves can create an even greater, more powerful whole.
Or team up to cause as much chaos as they can to get back at being ignored for so long.
When Jack Frost was "born", he had no memories of his original name or who he used to be. The trauma of his sudden death blocked them, and the continued trauma of being isolated prevented them from ever being released.
Unknown to Jack, his darker twin had also been born into the world. However the light from the Man in the Moon was to bright, and so it remained shapeless. Unformed.
So it waited, and gathered strength. It watched Jack, occasionally lending it's powers and companionship through the Wind. Wind, who was the only force that could hear either of them or ever paid them more than a cursory notice.
For two hundred and eighty years, the darker version of Jack remained dormant, formless.
Until it found a physical body to take over and shield itself from the Man in the Moon's light. It had no idea that possessing an unborn infant would expose it to the infamous Pitch Black. It just wanted to exist...to give Jack someone he could talk to.
Seventeen years later...
He was pissed. For the past seven years, he had been friends with these two idiots, put up with the bickering, the insane study schedules, the horrible manners and personal habits, and the way they created a barrier that kept nice, friendly people away from him.
But this? This was the last straw.
"So let me get this straight. You're telling me that you want to quit?" said Harry far too calmly to express how he really felt.
"You don't have a plan, and I'm sick of having to skulk about everywhere just because you want to go on a stupid treasure hunt!" said Ron loudly.
"I hate to say this Harry, but Ron has a point. Perhaps regrouping with others would be a nice break..." said Hermione, completely missing his expression.
"If you want to snog or shag, all you had to do was say so and I would have given you two your space for a few hours. All I would have asked was that you clean up after yourselves. But this? This is a new low for both of you," said Harry, his eyes flickering ominously.
The two stepped back at the cold chill in his words. Neither had noticed until now how cold it had gotten around the tent...it had warming charms to keep winter's chill away.
"Mate?"
"I'm not your friend, I'm not your anything," said Harry with ice. He pointed at the door. "If you want to leave so damn badly, there's the bloody exit."
Ron stared in shock, before that quickly turned to a glare. He stormed out the tent and apparated away. Hermione cast a glance between him and Harry, before following. She needed a proper shower and a meal that was cooked properly before she planned to rejoin Harry.
Neither of them realized the critical error they had just made.
Harry took a deep breath, trying to calm his anger. It didn't help.
Instead it only made his cold rage worse. So he decided to do the one thing he had been tempted to do since he found out about the Taboo. And without his friends there to silently judge him, he could finally let loose and not care about the consequences.
It wasn't like there would be any SURVIVORS after what he planned to do.
He threw up some anti-appartion and anti-portkey wards that would keep people from leaving once they arrived. Once he was sure they were established, a vicious grin appeared on his face. Unseen by humans, his eyes went from bright green to a bright gold color. His hair became darker, more ominous and his wand seemed to buck in his hand. It didn't like what was about to happen, or it didn't like his true nature.
It took him a moment to realize his hands were becoming cold, but he didn't really care. Nor did he particularly give a damn about the fact that the ground beneath him had frozen over rather solidly, yet he could walk without slipping.
He took a deep breath and said "Voldemort, Voldemort, Voldemort."
It was almost like he was playing Bloody Mary, only in a far more vicious manner.
Like clockwork, Death Eaters arrived to teach whoever dared to say the name out loud a lesson.
What they got was a bloodbath.
Freed of his personal hang-ups, and unaware of the power that was waking up inside, Harry went to work casually slaughtering anything in his path. Death Eaters scrambled to kill him first, using dark spell after dark spell, only to find their footwork less than stable as frost spread across the sudden battlefield. Spears of sharp ice would impale their arms, sudden patches of ice would appear where they were about to place their feet causing them to slip and crash into rocks...oftentimes with fatal consequences.
Without warning Harry's wand decided to protest the abuse, for it's core was made of a fire creature, and his true nature was ice and winter's touch. It burst into flames with a sound of phoenix song. The wood didn't really survive the sudden inferno.
Rather than stop, Harry chose to exercise his newly found control over ice and snow and killed the left overs.
At the end of it, he wasn't even breathing hard. Instead, he was laughing. Long and hard with genuine mirth.
Seventeen long, painful years of being treated like everyone's plaything. Seventeen years of being both ignored and ostracized by the people around him, all because he was different in some way. Seventeen years of hiding his true nature to the world at large.
Never again.
Harry's eyes glowed like golden orbs of death, looking around him at the carnage he had inflicted, and he felt something snap inside him. Something that had been hiding, waiting for the perfect time to awaken. Hindered by his wand because it was born of a creature of fire and rebirth.
Harry held up a hand, and saw the snow that formed from his palm. He threw it at a tree, causing it to freeze over upon impact.
This was his true nature. This was the power that had slept until he was ready to accept it.
He was not the playful Jack Frost, who brought winter's touch to the children and created snow days.
No, this was Night Frost, Jack's darker half who brought winter's cold unrelenting fury to those who dared to attract his ire. He wouldn't harm children under ten, but those that thought they could escape justice because of power, money or influence... they would soon find his wrath far more terrifying than anything they could create.
Night Frost smirked.
It was time he got to work cleaning up the mess the adults had left for the children to deal with.
The cold terror Night Frost left in his wake put Voldemort's efforts to shame. Whenever he appeared, he left death and icy destruction in his wake. However unlike Voldemort, he never harmed the children. Instead he left them in cold cocoons until he was done and made sure they never saw what was left of their foolish parents.
For those that bore the Dark Mark, they quickly found themselves outmatched. The Sheppard's crook he carried became synonymous with death to those that served the Dark Lord.
Snape's death had been particularly graphic, even for them. His entire body had been speared through with anatomical efficiency.
Not a single organ had been spared.
The remnants of the Order of the Phoenix were scrambling to find out who this mysterious force was. Some to recruit it and possibly curtail some of it's more deadly efforts, some to put an end to what they considered mindless slaughter.
Everything came to a head when Voldemort finally caught up to the mysterious Night Frost, unaware that all of his soul fragments had been methodically tracked down and destroyed.
The final battle...
Voldemort sneered at this young upstart who dared to get in his way.
Night Frost casually leaned against his staff, smirking.
"You know, you have no idea how big of a pain in the ass it was tracking Snape down just to kill him. And the expression on his face when he found out who I was...priceless."
Twirling his staff to create an even colder area around him, it was baffling how Voldemort missed the obvious. Then again the staff was black as night, not the bone white it had been when he first nicked it from Dumbledore's tomb.
By killing Snape, the three artifacts given by Death to the brothers had accepted his claim as their Master. Though even he would admit to being surprised when the Elder Wand turned into a staff with a crook at the end and became pitch black in color.
He also didn't know who to ask about why the staff itself seemed to gather shadows and black sands if he allowed it to do what it wanted, rather than follow HIS command.
He inherited the cloak from his father, gained the stone after Dumbledore disposed of the soul piece, and once he killed Snape, the wand accepted him as a new Master.
Though he would be teaching the damn staff who was boss after this was over and he was in seclusion.
Voldemort's sneer never abated as he started the fight. The deep purple hex was easily avoided, though he did manage to hit Night with the killing curse that had hidden behind it.
Everyone watched with baited breath as Night took the Killing Curse head on. For a few moments, it looked like the curse had done it's job.
Then Night started to laugh. It wasn't a good laugh, far from it. In fact it filled the heart and souls of anyone hearing it with dread.
The staff in his hands seemed to glow an almost luminescent black, and the mood seemed to gather the clouds around it to hide the view of what was about to happen from it's gaze.
Darkness and the coldest bite of winter's chill gathered around Night Frost, and suddenly you could see something in his eyes that filled even the Dark Lord with dread.
He hadn't killed Night Frost with that curse. He had liberated whatever was holding the bulk of his powers in check.
Until now, Night had been limited by his mortal constraints, put there because he had been born to a human shell. His mother's sacrifice had kept them bound, but only by a flimsy tie that could be broken if the conditions were met.
Voldemort had accidentally destroyed that lynchpin, and the last remaining soul piece that had been sitting quietly away in the teen before him.
He had created a spirit of dark and ice.
Night's smile did not give anyone good feelings. Instead they inspired all the fear and terror that came from primordial instincts forgotten, but still very much alive.
The fear one had in the cold nights when the wolves prowled around them. Of feeling darkness creeping into their souls as their body shut down from the howling winds of winter's dark embrace. Of being lost and alone in the cold as the wind raged around them and snow fell so thick you couldn't even see where you were, or if you were heading to shelter at all.
The kind of cold that left cavemen huddling in the far reaches of their pathetic shelters shivering while trying to keep the fire going, knowing instinctively that to lose it would equal an instant death sentence.
In short Voldemort had just liberated the embodiment of winter's cold unforgiving Wrath.
And he had a rather large grudge against wizards in general and no real reason to hold back.
If Night had ever met Pitch Black, there would be some uncomfortable comparisons made between the two. The worst part was that after this, Night would never have the same problem that they had with belief.
People believed he existed because he killed one of the worst Dark Lords in history, and thanks to Voldemort's stupidity he was now effectively immortal. The same status that the man had tried to gain himself!
"Shall we get started then?" asked Night far too cheerfully and with such a disturbing smirk that it would haunt people's nightmares for days.
Several weeks after the final battle...
Night was casually leaning on his staff, having finally exorcised whatever it was that had caused the thing to misbehave while he tried to use it.
As a nice perk, he could now fly without a broom. It seemed that by forcing the staff to submit to HIS control alone, he had gained a modicum of control over the Wind itself.
The wind was now curling playfully around him, lifting him higher than he had ever dared to fly before. Yet he didn't feel an iota of fear that he would fall and crash. He was by all technicalities dead after all.
Not that it stopped the goblins. They had taken one look at his eyes and basically shunted all his gold and holdings to the "Frost" account, rather than piss him off. In exchange he agreed not to turn their entire bank or the goblins inside into ice sculptures that would never melt without at least giving them a warning with enough time to placate and fix whatever they had done to get on his bad side.
Night was having so much fun that he was completely blindsided when something quite literally crashed into him several hundred feet above the air.
One moment he was gliding and having fun with his newly liberated powers, the next he was crashing with another awkward body into the trees.
"Watch where you're going, you bloody idiot!" shouted Night once he gathered his wits.
The youth beside him had snow white hair and pale skin. He was wearing a worn hoodie that was a shade lighter than the one Night had on, and pants that were threadbare and worn. He also had no shoes on, though Night could commiserate with that.
He liked the feeling of dirt under his feet.
It took the other youth a moment to get over his surprise at crashing into someone, before he realized something more important.
"You... you can see me?" he said, almost as if not daring to hope.
"Of course I can see you! Honestly, I'm surprise that people haven't commented on your hair color yet! You look like an old man!" said Night, a little less cross. The kid sounded very lost, and he was a sucker for children.
While this teen had snow white hair that looked like an old man, Night had dark black hair that seemed almost the polar opposite.
"You can see and hear me?" said the teen, looking almost overjoyed with the idea.
Night gave him a more thorough look, and he remembered something he heard from the goblins about his new predicament.
"You're Jack Frost, aren't you?"
Seeing how over the moon the poor winter spirit was that someone finally acknowledged him, Night couldn't help but feel some sympathy for the guy.
He knew what it was like to be alone in a crowd full of people who couldn't really acknowledge you. It was bad as a human, but for spirits it was ten times worse.
"Yeah! That's me, Jack Frost, the spirit of winter!" said Jack happily.
"Call me Night Frost, spirit of winter's cold fury," said Night, holding out his hand. Jack seemed to revel in the idea of shaking someone's hand. Then what he said caught up to him.
"Night Frost?"
"Think of me as your darker, more vengeful doppelganger. You bring the fun of snow days and cold play time to children, I use my powers to insure those that hurt them never get a chance to do so again, despite any power they might have," said Night dryly.
Jack seemed to take the idea in stride, still rather giddy at having SOMEONE to talk to.
Up above, the Man in the Mood decided to observe the two closely to see if intervention was needed.
Night Frost was still too new to get a good read on how he would turn out.