Jack Frost didn't know much about anything, and that included himself. The only thing he knew for sure was his name. He quickly learned some of his powers: creating frost, making it snow, making it colder. He learned that he did these things with the staff that had been on the lake he woke up on. But beyond that, Jack knew nothing. He didn't know what he was supposed to do with his powers, or what would happen if he didn't. He didn't know what would happen if he didn't let the wind take him and his snow across the globe. He didn't know whether his coldness was supposed to be bad and freeze crops and kill things, or good and make snow days and have fun, or just neutral and chaotic and indifferent.
Jack didn't know much about himself or his powers. He didn't know whether he was supposed to do good things or bad things or if it mattered either way. All Jack knew was his name and some powers, and that was all he knew for a very long time.
Jack didn't have much direct interaction with children. Or anyone, really. But it was the children that mattered most to him, the children that didn't believe in him, didn't see him or hear him or know of him. It was the children that mattered to Jack, the children that, unlike the other spirits, liked what he did. His fellow spirits could see Jack, could talk to him and listen to him (not that they often did). But the majority of them hated the snow, hated the ice and the cold and the fun they called chaos, and the rest saw his snow as competition to their own winter weather.
The children couldn't see Jack. But they could feel his effects, and appreciate them. They could react to the weather and to the snow and, in essence, unwittingly react to Jack. Jack took personal pride in every snowball fight, every sled ride, every snowman built by children with his snow. He relished in being the cause of their laughter and joy on a surprise snow day. Even if they couldn't see him, Jack felt that the children loved him. At the very least, they loved a major aspect of him.
Jack Frost, however, was not all fun all the time. There were bad moments, bad days, and in the beginning there were even some bad years. Sometimes, Jack would be overcome with loneliness, or with anger. Anger at the Moon who abandoned him, the children who didn't see him, the spirits who hated him. Sometimes, that anger would dissolve into depression, a sort of hopelessness that Jack was sure would never end. And sometimes, when that depression did end, Jack would be left feeling hollow, feeling apathetic and detached from the world around him. Feeling dead.
Magic was difficult to control, especially for novices and when wielded under emotionally charged situation. Jack happened to fit both criteria. His youth, in terms of physical age, emotional immaturity, and length of existence, ensured that Jack would never really fit in with other spirits. The last spirit created before Jack was created centuries before him. By the time Jack came along, everyone had their social circles and friendships filled. Besides, no one wanted to deal with a volatile, dangerous new winter spirit.
In the first years of his life, with no direction from other spirits, Jack's powers were controlled nearly entirely by his emotions. When he was angry, freezing blizzards and hail rained down on icy streets. When he was depressed, thick snowflakes could fall in one town for weeks, suffocating the people under thick grey clouds that never seemed to dissipate. His hollow state was considered by many to be the worst. Without focusing his powers at all, Jack allowed the cold to overcome him, to become him. He would acquiesce to the wind's force, letting himself be dragged from town to town, letting his snow and ice ooze from him like blood from a wound. Without trying to control it, Jack's powers would plunge temperatures into the negatives, would cover towns in sheets of ice and snow, silencing them with the rest of the world. And Jack, for a time, wouldn't care. He couldn't care, couldn't let himself care anymore about what the children thought. It always ended in heartbreak.
Those times always ended. And Jack would always regret those times, when anger and sadness and emptiness wreaked havoc on the world. Jack would regret letting his cold hurt people, hurt children. He would regret turning snow in to something dangerous and deadly.
And most of all, he would regret the fear.
"What goes together better than cold and dark? We'll make them believe! We'll give them a world where everything, every thing is-"
"Pitch black?"
"And Jack Frost, too. They'll believe in both of us."
Jack didn't know what it was like to be believed in. It was an experience that he feared he would never have. To have a child believe in him, see him, hear him. To have someone who would throw a snowball directly at him, instead of through him. To have someone who would talk not just about the snow, but the bringer of the snow, someone who would talk about Jack Frost.
Three hundred years, and Jack had never figured out how to accomplish anything near that. Three hundred years, and nothing to show for it, no believers to speak of. Not that anyone would ask.
Pitch was offering him a solution. A surefire way to make children believe in Jack, to make them see him. Jack had imagined such situations before, imagined children laughing with him, having fun with him, being happy with him.
But belief was not the same as being liked. Being believed in would not ensure Jack's position as a fun-loving bringer of snow. And if he helped Pitch, he wouldn't be that fun-loving, happy spirit he wanted the kids to believe in. If he joined Pitch, that happy, joyful version of Jack would be dead.
When Jack lost control over his emotions and, by extension, his powers, the results were often devastating. The regret Jack felt was only compounded by the children's reactions. They would no longer look forward to snow days; instead, they would cower inside, memories of bitterly cold blizzards scaring them away from the snow. Jack had ruined snow and cold for countless children.
When children loved the snow, Jack felt loved. When children hated the snow, Jack felt hated. But he was used to hate, that came with the job of a winter spirit. No, the worst of all was when children feared the snow. When children feared Jack.
He would rather be loved and invisible than known and feared.
"What goes together better than cold and dark? We'll make them believe! We'll give them a world where everything, every thing is-"
"Pitch black?"
"And Jack Frost, too. They'll believe in both of us."
"No, they'll fear both of us. And that's not what I want."
Jack did not know much. He didn't know if his powers were supposed to be good or bad, or just simply chaotic. But one thing that Jack did know was that, regardless of his powers, he did not want to be bad. Jack Frost did not want to cause fear. This wasn't an unquestionable fact like the rest that he knew, as much as it was a fact he figured out about himself. Jack Frost didn't need to be told by the Moon who he was, or what his purpose was. He decided for himself that he was not bad, that he didn't want to be feared. Jack would make his own purpose from there.
I have been trying for days to write this and it was not cooperating with me. I still kind of hate how it turned out. It's just, the idea is still really interesting. Pitch was offering Jack the one thing Jack wanted most, and he didn't take it. Because he didn't want to be feared. And, knowing Jack's powers, I'm guessing he's probably had some experiences with being feared before. Someone else should write this better. Someone who can write in a sane and logical manner.