He hadn't seen it at first. It wasn't until afterwards – until after Cuba, after he'd already lost Charles – that he realised what it had been all along.

"Somewhere between rage and serenity."

Rage itself was clear. Rage was everything that had happened since he was a child and the soldiers came. Rage was the death of his mother, the calm little smile on Shaw's face, the numbers branded into his arm. It was humanity, and everything they had done to mutants – it was their fear which turned so easily into brutal hatred, into the need to wipe out everyone who was different, but to understand them first in the most cruel and painful ways. Rage was every mutant child growing up in terror because of who and what they were.

Rage was easy. He didn't have to try in order to summon rage; it was always there, just below the surface even when he was asleep. Rage came naturally.

Serenity was something else entirely, and that was what he had taken so much longer to understand. It didn't come easily to him. But now he could find serenity, when he wanted to – it was in that memory of his mother, in the time before everything had gone so utterly wrong. Back when there were things other than fear and loss and anger in his life. When there was love, too, and hope. That was serenity.

But who had found that memory for him? Who had given him emotions he had thought were long since lost?

Charles was serenity too, and that was the most painful thing to realise because he saw it too late. Serenity was a drink and a game of chess that lasted into the small hours of the night. It was conversations about life and science and what they should do for dinner. It was being told they could be something more, make a better world together, and almost believing it.

He would never tell a soul, but when he searched for serenity now, it was Charles that he saw. Charles sitting in his study with a cup of tea, his face eager and his smile wide as he drew Erik into discussion about the school for mutants he already envisaged.

And when he understood, he could see that this was how it had been all along. To use his power he had to find the balance between rage and serenity; to decide how to use it, he was forever torn between retribution for every crime committed against mutants, not just in the past but every one that would be in the future, and Charles. Just Charles, on the other side, telling him to be the better man.

It was strange to realise, too, that this was how it was always going to be. He was so many miles away from both Westchester and Cuba, so far from the places where serenity could have claimed him and where rage won the battle in the end, and yet he knew that this was how it was going to be every time he used his mutation from then on. Charles had not been able to change him and yet he had, in a way.

Because rage was always going to win. He knew that, had really known it all along, which was why he had tried to make Charles understand that he was fighting a losing battle. But Erik had been wrong too, because he had thought that rage was the only thing he had left. That it was all there was and all there would ever be.

But now there was serenity too, in the life of a man who was thousands of miles away. And despite Charles' pain that day in Cuba, despite the helmet and despite everything Erik knew he still had to do to protect the mutants, that serenity was always going to be there.

Charles was always going to be there, in the brightest corner of his mind.