omggg. i think they like to talk nasty generally but nastiest.... i think its the breeding kink 😭 i MAYYY be biased. also, somehow it is more nasty (/pos) when they are in bodies where impregnation is not possible. like "oh you're so crazy about me you will break reality itself to leave me with child????? you're going to fertilize my non-existent eggs?? wowwww 😫" so charles begging erik to get him pregnant or knock him up, not to pull out, to keep his cum inside him "so it takes", erik telling him he looks fertile or saying he's going to fill him with his seed

specifically for 616, i also think the unabashed way erik talks about charles' body really turns him on, as someone who is more reserved and has spent so much time within a respectable persona. talking about his fat ass and his fat nipples or telling him he looks fertile and breedable...how he just wants to sink his teeth into his ass, lick him from hole to balls....it makes charles blush, and it also makes him dribble pre uncontrollably 🥰

i also think 616 charles has a bit of a humiliation kink and enjoys being called a slut. though, im not sure they'd use those words too often bc they're old — so words like "whore", "tart", "slag", "minx". always lovingly, teasingly, a little something to make charles moan, unless they're doing a whole bdsm scene about it

yes!!! omg i luv talking abt omegaverse physiology + how it affects omegaverse cherik's everyday....which is why this answer is SOOOO long... hope u enjoy regardless

generally ruts can happen for a multitude of reasons but the most common ones are:

• randomly a few times a year for younger unmated alphas
• triggered by an omega's heat, especially if the alpha is mated to the omega
• an alpha stud (a mature alpha that has bred their omega multiple times + has been changed by the hormones + pheromones from that) hasn't knotted their omega for an uncharacteristically long time

first a rut will come on with just feeling weird, usually progress to a headache, fever + sweating, shakiness, and this feeling many alphas describe as an "itch under the skin". once the rut is getting into full swing, an alpha will start putting out an intense rut scent, and the alpha's genitals will begin to swell. the cock gets perpetually hard + swollen, especially the knot, and the balls usually swell up as well + hang lower. alphas usually feel an uncomfortable or unbearable tightness or pressure in their genitals that, the longer they don't attend to it, begins to become painful.

the cock will start reddening (on whichever parts redness may be visible on their cocks skin), drooling a lot of precum and throbbing visibly — it's just a monster erection that will not go away. thoughts usually become overwhelmed with sex and breeding above all else, eschewing food and water, and most unmated alphas will spend at least a day jerking off/fucking cocksleeves/etc until the rut slowly starts to dissipate.

the ruts for alpha studs are all of that, but even more intense + thus more painful. thankfully they have their omega to turn to, and don't have to struggle with masturbation devices that aren't giving them what they truly need. ultimately the goal of a rut, what is consuming an alpha's thoughts, what their cock is straining for, is to knot. to breed. it's like the knot is acting out bc it's not been neglected, or like it's pent up. so alpha studs will fuck for hours and fill their omegas with cum but still not be satisfied, still not able to knot. achieving a knot is what ends or at least begins to taper off a rut for alphas, similar to how being knotted does the same for omega's heats!

SO for erik. he and charles have an active sex life but with all their kids they're often become very busy with them, and sometimes charles gets very busy with his work (he's sort of a stay at home dad, he just. has his own state-of-the-art research lab in his house lol). and knotting takes time, so when they do fall into each others arms whenever they have a quick moment of peace or the end of the day, erik doesn't push his knot in, or he just eats charles out, or he just face fucks charles and comes down his throat with his knot pushed against his lips.

and because erik tends not to prioritize self-care and because charles loses track of time so easily, they've been doing that for months. so, erik wakes up with a pounding headache, thinks nothing of it, goes to work, and then its two hours later and he's locked in his office drenched in sweat and dribbling right through his pants, calling charles and telling him he's in rut and he's going to come home early.

and charles starts scrambling bc he knows what a rut means — which makes him, immediately, very wet, but he also knows that it means he needs to take care of erik and prepare. it's a bit like how alphas care for omegas during their heats. they're going to be fucking freak nasty for hours, he needs to make sure its comfortable and that they stay hydrated and fed.

he calls raven to get her to pick up the kids from school and have them sleep over at hers and irene's, fills up some water bottles and gets some snacks to put in the bedroom mini fridge, stocks the bedside table with wet wipes, dresses the bed waterproof blankets and takes a quick shower in record time. and ofc, also puts on something cute. and incredibly skimpy. for flavor

any alpha is singleminded in this state but i think erik is very singleminded when he's far into rut. he just opens the door and charles' scent hits him, and he just stalks over, gropes the soft ample flesh of his tits and thighs so hard it stings, picks him up. the rut brain fog is kicking in and he can barely focus on what charles is talking about bc he can smell his slick already rolling down his thighs and his cock feels like its about to burst if he doesn't get in his pussy and past his cervix and into his womb —

thats all very intense for a telepath who is halfway to being triggered into heat by rut scent to hear of course. charles just abandons trying to get erik to drink some water or have a protein bar before they get down to business and just lets him carry him to the bedroom, press him into the mattress, and slam his fat swollen girth inside him

even though erik is very sexually aggressive + dominant in this state he's paradoxically quite whiny. like he's already a "will beg for pussy if pressed enough" type soft dom, but in rut if charles so much as cockteases him, he'll start whining and humping him like a teenager. bc it does hurt and he needs him and he's been waiting so long. so charles takes a lot of pity on him and just lets him take his pleasure.

and that's fine by charles, bc when erik fucks charles in rut its so intense + so rough that he couldn't possibly be bored. charles is on some mindbreak type shit bc he's come and squirted and gushed more time than he can count, and erik isn't even on his third orgasm. erik's refractory periods are even significantly shorter so he's always raring to start pumping inside him again.

erik already shoots big thick loads, but during ruts thats exaggerated. so charles is so full of his cum and it's just rolling out of him, his cervix is fully battered into submission, and his whole lower body is throbbing with pleasure....in a rare moment of lucidity he thinks about how he's not on birth control, and how alphas are considerably more virile during heat. how there's no way he's not being impregnated right now, he swears he can feel if happening. he can barely start thinking about the logistics of another litter when erik is gasping and shaking and rolling his hips so deep inside him that it hurts...and then his knot pops in and is finally, finally swelling up, fast.

during ruts alpha's knots get far bigger than they usually do. so charles is feeling the stretch hard. not just in his cunt but deep inside him, bc a knotting load is always bigger than a regular load, and the same goes for a rut. his tummy bulges out some and he's just clinging to erik, eyes rolling back as he goes breeding-dumb

a rut knotting is a weird experience for alphas because the pleasure is like no other but it's so much that it wrings out the whole body, that it feels like it hurts. the orgasm + ejaculatory period can look/sound like the alpha is in distress or pain. for erik it's mostly growling, whining, sad vocalizing + panting, and crying a little. charles always tucks eriks face into his neck and strokes his hair through it. soothes him with soft purrs and telepathic calming.

alphas usually come for a lot longer during this time, and for erik he's usually coming consistently for a couple minutes. then, still swollen and tied to charles for half an hour to a full hour, his cock intermittently twitching and spurting a jet of cum, especially if either of them moves too much and stimulates it.

usually after this exhaustion overtakes him, and erik will immediately want to pass out + sleep forever, but charles always keeps him awake long enough to feed him some water.

(also after another pregnancy charles is very susceptible to lactating, even when he's not pregnant and isn't in heat, so during future heats erik often begs (+ suckles) his way into just replacing any sustenance with charles' breast milk 🥰)

usually if knotting is completed, eriks rut dissipates into constant horniness (perpetually half-hard) + some feverishness the next day, and its mostly gone by the third!