Cold.
That's all he ever was. He was cold, always cold. It was the kind of cold that sank down, deep into his skin and settled into his bones. He couldn't get warm.
He tried. Oh, did Jack Frost try to feel warmth. He curled up under blankets, drank boiling hot soup, put his hand over a lit candle. He walked straight into a burning building, once. Nothing ever worked. Anything he ate or drank cooled instantly. Any flame in his general proximity was extinguished in a puff of steam.
But he never shivered. Never, even when he was in the middle of an Antarctic blizzard. Because that cold was just physical. It was temporary, passable, ignorable.
No, what he felt was different. What he felt was worse, so much worse. The cold he felt could only come from dying. He had drowned in an icy lake, but he hadn't stayed dead. He had come back. But he brought with him the icy claws of death.
He didn't need to eat, or sleep, or even breathe. His heart didn't beat, his blood didn't pump through his veins.
He was numb. He didn't feel. He couldn't feel. He was hollow. A shell. A shadow of what he had been. It had been there from the time he had risen from the lake, but it was only solidified when he went to the village. The first time someone had walked through him. The realization that he was invisible, unseen and unheard by all.
And then he found some that could see him, hear him. And they rejected him. They turned him away, cast him out. So he left. He flew away from humanity, from the other spirits. He flew to isolation.
And he found solace in the cold he so hated. He flew to the Antarctic, a deserted wasteland. He stayed for years, too many years for him to bother counting, before he returned.
He created a mask for himself. He put forth a carefree, fun-living attitude for all to see, carefully burying himself under an endless series of pranks and snowball fights. He couldn't let anyone see the real him, because that would mean getting hurt again.
Even if they got through his first mask, they wouldn't see past the second.