Disclaimer: They're not mine. They're also not usually this gay, or this naked, so if that’s not your thing, move along. This was one of eight drabble challenges posed to me; Caro Dee asked for Favorite Spell.
Perpetuo had been Lucius's favorite spell; a way to prolong the agony of Cruciatus or the delight of orgasm indefinitely. It had been a test of one's mettle, to see if one would break after one's balls were empty and nerves were frayed by pleasure beyond the threshold of sanity. Severus saw no reason to deny himself the experience simply because he and Lucius had long since parted ways.
"Are you sure about this?"
Fighting to retain an iota of self-control, Severus was gratified to discover he could still summon up a withering tone. "If I was not sure of you, you flea-bitten cur, I'd choose a better moment to mention it than when I'm stark naked with your wand pointed at my privates."
Remus had the audacity to chuckle at that and press a kiss to Severus's belly. "Just giving you a chance to change your mind, Severus." And with a last, careful scrutiny of Snape's features and a reassuring smile, he laid the wand down a moment and used that hand to guide himself home into Severus's body.
Snape tossed his head back and forth, clenching his abdomen in a futile effort to reject the intruder, but his traitorous body arched and welcomed the werewolf deeper inside as it always did.
Catching the usual signs of surrender, Remus planted another kiss against Severus's calf and began to move, picking up his wand and balancing his weight on Severus's raised thighs, jackknifing his lover deeper into the mattress. He hated this part, he did, arse over teakettle like an infant on a changing table, breath squashed out of him with every thrust, the sharp, invasive pain that made him squeeze his eyes shut and hide from the open joy in Remus's face. He felt fingers near his groin and batted them away, taking himself in hand. That was better, he thought, unable to repress a grunt of pleasure at the familiar hot and sweaty grip. But Remus's cadence battered his defenses, changing the rhythm of his hand, his breath, his heart. Remus was warm and loving, inside him, around him, impossible to fight as the ocean tide. But he had to fight, had to keep this one last reserve safe, and his hand sped up on his shaft, trying in vain to outrace Remus's thrusts...
"Severus," said Remus, and Snape fought not to answer, not now, when his whole body was tensed and quivering on the edge -- "Severus."
His eyes snapped open, saw the wand pointed at his groin, the golden eyes locked with his own, and his eyes went wide with panic and denial. No, not like this, please, he'd changed his mind--
"Perpetuo," Remus whispered, as a final, deep thrust shoved Severus over the edge.
The orgasm started in his balls, tingling, shooting to his groin, then continued to build, a sea change of pleasure through his cells. He could feel the endless spattering of wet heat on his belly, but he was scarcely aware of it as he groaned shamelessly and tried to impale himself again and again on Remus's cock. Merlin, he was going to break his own fingers, clenching the sheets this hard. The pleasure felt like it was cracking his chest open and he was too far gone to feel ashamed when he started crying, begging Remus to stop, it felt too good to stand, like every part of him was safe and loved and open, as the orgasm crashed over him again and again, grinding his body and mind to dust and making him crave more...
"--nite Incantatum. Did I hurt you?" Remus asked, the worry in his voice unmistakable. "You should have told me it did this to you!"
"Doesn't... do this," Severus managed between sobs. It was supposed to be fun. There was nothing remotely fun about having the momentary crack Remus had made in his defenses magnified beyond all reckoning.
Remus stirred, to get the light or some water, for all Snape knew, but he cried, "Don't leave me!" before he could stop himself, shivering against Remus's inhuman heat.
"I won't," Remus promised softly, wrapping him in the warmth he hadn't needed an hour ago. "I won't leave you, love. I promise."
End.