The brain doesn't feel pain, per se. The brain doesn't have any pain receptors; it's the reason why doctors can perform open brain surgery.
So Charles knows damn well it's not the pain from Shaw's brain that's hurting right now; yes, the coin being pushed through skin and skull hurt. But they're past that now. No, the coin is somewhere in the frontal lobe at the moment.
He knew what Erik was planning on doing the moment he saw that coin. He didn't lie when he told Erik he saw everything that one fateful night when they met each other. He also knows he wasn't planning on stopping him; he knows Shaw is a danger for mutant and humankind. He may not like killing, but that doesn't mean he only sees the good in people. Shaw is bad.
But Erik put on the helmet anyway. That was enough to hurt the trust they built between the two of them.
The pain is immense. Not because of the coin slicing through Shaw's brain. No. Because his mind, his gift, is holding on to someone who's dying. Someone whose brain is shutting down, someone who's past saving now as the coin makes its way to the end of the frontal lobe, and focus Charles, Erik needs you, the frontal lobe only controls motor function, problem-solving, fuck it hurts, one more Charles, keep your mind in the game, memory- not enough to stop shaw from attacking Erik if he lets go.
And oh. The parietal lobe. Someone's screaming. Maybe it's Shaw. The... the parietal lobe affects... it... it controls the wait no... oh. It had something to do with sensory input. Yes. Warm. Cold. Sensory input.
By now his own mind is slipping. He can't seem to think clearly, he can't seem to get out of shaws head. He's stuck, he's stuck in a dying body, and not only Shaws body is losing its function but so is his and his mind is shutting down and something's dripping from his nose and he can still hear screams and he's dying isn't he, he's dying and he can't stop it. There's no way to stop it because he's stuck.
He just screams and screams because it is him screaming, he didn't notice at first but it's him, and he can hear Moira is frantically trying to get him to respond but can't she see he's dying? He's going to die. Well... rather him than Erik.
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The coin comes out of the other side of Shaw's head, falling to the ground now that it's freed from Erik's power. Erik looks at it for a few seconds, before looking at the lifeless body of the man who killed his mother, the man who ruined Erik's life. No more. Never again.
He uses the metal of the submarine to float Shaw out of the submarine, using the metal in his clothes to float as well. He lands just outside the submarine, unceremoniously dropping Shaw on the sand. "Today our fighting stops!" He shouts, his voice strong and unwavering. Until he notices Charles isn't there. And neither is Moira or Raven.
The jet. He has to check up on Charles; did he get hurt somehow? He abandons his speech, his cause for now. If he has to choose between his cause and Charles he'll always choose Charles. Without a doubt.
he runs towards the jet, panicking when he sees Charles on the ground with his head on ravens lap. "We don't know what happened." Moira starts, the second he steps foot in the jet. "He just... started screaming, and he collapsed and now he's like this..."
He falls on his knees next to Charles, gently taking him over from Raven. He makes sure the younger man is comfortably resting against his chest, his fingers ghosting over Charles's pulse point. Just to be sure. "What happened." He growls, looking at Moira "you were supposed to protect him."
"I... don't know! He was connected to shaws mind, told me he had to focus, said something along the lines of damnit Erik... and he just collapsed and started screaming. I got Raven, to see if it's something that happens more often but then he just... collapsed." There's a panicked look on Moira's face, a look he initially sees as fear for Charles's life until he notices the jet is vibrating. Oh. That may be on him.
He forces himself to remain in control, to stop the jet from vibrating. He needs to take control of the situation; there's... kids, depending on him after all. It would look bad if Charles wakes up and the kids are frightened. Yes. Okey. He slowly gets up, Charles in his arms. They need to go home. "Raven, fetch Azazel from outside. It's about time we went home, we have finished our business here."
He carefully adjusts Charles in his arms, making sure the telepath is comfortable. Or well, as comfortable as he can be. There's a trail of blood dripping out of his nose, and it looks out of place on Charles's face. He's the one who gets beat up, who comes home covered in blood. Not Charles. It doesn't work that way.
He looks up when Azazel enters the downed jet, a set look on his face. "You picked the wrong side. But you've got the chance to change that now. We need to get home, and soon. I can feel the weapons on the ships being loaded, they're going to blow us all up. So, we need your help. We offer you a safe place to stay."
Azazel merely nods, holding out his hands. They all stand in one big circle, Raven holding onto Erik. They're going home, and Charles will be okey.
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“Erik, you can stop coddling me. It’s been a week darling.”
“I’m not coddling you.”
“Honey. This is the tenth cup of tea you made for me today. It’s barely past noon.”
“Yes. You have to stay hydrated!”