Erik keeps everything -- body, mind -- under wraps, leaving Charles no choice but to find other outlets for his desires. When those desires cut a little too close to home, though, everything comes out into the open.

Very quietly, Charles says, “Can you show me?”

“No.” Erik looks at him again, then, his expression as steely as Charles has ever seen it. His resolve is even stronger than his pain. “To show you this would be to make you share it, and I would never do that to you. Never.”

In which Erik is the son of servants, Charles is the son of aristocrats, and hedgehogs make repeated appearances. -- Modern AU that is clearly inspired by Atonement (minus most of the angst, that is).

Many of the pressures in Charles Xavier's life -- the sacrifices Erik and Charles make to be together -- the constant tension of being closeted -- Charles' relationship to the Church he once served as a priest -- his distance from his sister -- come to the forefront in 1967. Because in that year, for Charles, peace is no longer an option.

Charles and his BFF Tony Stark have the life - they're co-valedictorians at the most prestigious high school in the city, they have their own condo in Manhattan, and they get to go to all the awesome parties. Charles just wished he understood relationships and sex as well as Tony does. His theoretical bisexuality starts to feel a lot less theoretical when he and Tony end up in Professor Lehnsherr's Physics III course at Columbia University, but Charles' decision to take their relationship further leaves both student and professor with more than they bargained for. Features an enthusiastically-consenting!16-year-old!Charles.

Charles liked to tell people that the first time they met, Serik punched a kitten. (Or, the one where Erik is an angry Vulcan, Charles is still a telepath, and grief still shapes their lives.)

Basically, Charles Xavier needs a date to his tenth high school reunion. Enter Erik Lehnsherr, Raven’s best friend, who happens to be a model and the new face of Calvin Klein.

They both know that neither would ever betray his ideals or force the other to do anything, but everytime they meet Charles secretly hopes Erik will kidnap him and Erik secretly hopes Charles will brainwash him into coming back home.

In 1965, Erik Lehnsherr has infiltrated the NYPD for his own purposes -- but his powers make him a brilliant detective. Yet that's not why FBI agent Charles Xavier has sought him out. It's because the mysterious killer they're both trying to find is murdering people like them: other mutants.

Their search for a madman binds them together. Their inner demons may tear them apart. But the greatest danger comes when the killer they're looking for looks back ...

"I do believe the two of you were in the same year as boys, were you not?" Headmaster Shaw said. "Charles is the most competent deputy any headmaster could ask for, Erik, and he's been doing this for years…" He trailed off, as if finally noticing something odd in the way his Potions and Divination masters were staring at each other.

"Of course," Charles said quickly, his voice only a little hoarse, and stuck out his hand. "Welcome back to Hogwarts, Erik."

“Someone really should put up a warning on the city website,” someone says from high above. Raven cranes her neck and, of course, there’s Erik, crouching on top of the lamp post like he is the goddamned Batman. “Do not approach. Slayer on the prowl.”

Father Charles knew.

If you went to him, whether in the confessional or for an informal chat over coffee, he somehow always knew what was troubling you, even before you said the words.

Charles had never before considered himself to be a fan of smoking.

Erik is a fisherman who lives in a cottage by the sea; it's a quiet, secluded life, and he enjoys it that way. Charles has a bump on his head, with no memory of why he was dangling off the side of a dock, unconscious and nearly frozen to death.

Parody endings to An Ideal Grace (aka how Erik could have found out, but didn't).

Erik Lehnsherr is a visiting professor at Columbia University, as well as an acclaimed and award winning poet. Charles Xavier is a lead researcher with the Genetics Department who is well on his way to tenure. But what happens when Charles has to cancel a class because half his students abandon him in favour of a mysterious new English Lit professor? Naturally he ends up sitting in in the class, where Professor Lehnsherr mistakes him for a student. It's really too bad Erik has such a strict policy against dating students. It's also too bad Erik doesn't seem to know how to use Google.

X-Men AU, Good Omens-style, with Charles as Aziraphale, Erik as Crowley, Jean as the Antichrist, and Raven as a badass motherfucker.

‘Hey,’ the man purred, ‘you looking for a date?’

‘No,’ Charles said firmly, trying to keep his thoughts on his predicament. ‘I’m looking for my hotel. It’s called the Regent. Can you help me?’ He hadn’t met a whole lot of prostitutes before, but perhaps they knew about these things.

Apparently they did. They also charged unreasonable prices for directions.

Charles is a bright young thing, and Erik the society columnist who catches his eye.

“Oh, look! It’s Charles, and he’s been transformed into a cat by a malevolent government program! I wonder how I can change him back and thereby secure his love forever and ever, amen?”

After Magneto of an X2-ish future succeeds in the unthinkable, Charles sends his consciousness back to 1962 to guide Erik away from the path that will lead to the genocide of the human race forty years hence.

Charles knows that Erik has always loved him, and intends to use this knowledge + sex to seduce Erik away from his ideals in his youth.

There's no way this well-thought-out, sensible, debugged and 100% bulletproof plan can possibly go wrong.

"I should hit on a man who comes in every morning at seven a.m. in a five thousand dollar suit, says the exact same eleven words - and I've memorised them, by the way: the usual please, yes that'll be all, thank you very much. Looks directly at the person manning the checkout when he does it and does not manage to smile a single time, even when it's Angel. Rushes out as soon as he gets his drink. That's the person you want me to ask out."

An alternate universe (they're all not mutants, just human) where Charles is a social worker who fosters troubled kids, and one day he meets Erik, an ex-druggie/ex-convict (or whatever else, I leave it to anon to figure out which demons are chasing him) who reluctantly agrees to stay for only a while, but ends up staying for good and helping Charles to raise the kids. Awkward parenting ensues.

"Wow." Alex sat back in his seat, a little dazed. "So do you think your dad is...like..."

"...your dad's ex boyfriend?" Lorna finished with a wince.