He was the prisoner. She was the queen. They called him heartless. They used to call her a monster. He tried to kill her sister. She nearly froze her kingdom. He hid his powers for too long. She couldn't hide hers for long enough. He had seen doors closing all his life. She'd closed doors throughout hers. He wanted to cause pain. She was afraid of hurting someone. He had used love as a weapon. She had used it as a remedy.
When it was over, he wept, and she smiled. He was abandoned by his family. She was accepted by hers. He sobbed in an old, chilly cell. She laughed in the fresh, sunny meadows. He was fire. She was ice.
And just sometimes, their world would collide. He loved her. She loved him. It was enough.
Notes: I've wanted to write Helsa since...well 2014, so here it is! This mildly refers to the "Hans has fire powers" headcanon, but you can ignore that if you want.