Even after she decided she was up to trying it, there's still been the more practical question of how long she can hold her concentration. They've even practiced with other spells, Keyleth holding water up in the air and trying to keep it there while Vax did his level best to take her apart. She's never quite managed to hold it until orgasm, but she's gotten pretty close, far enough to say that they could at least have plenty of fun while she does.
Also, there was the question of how much she should change. That's ultimately up to her. At some point, she says, she probably will change her entire body into that of a male half-elf, and Vax has no doubt she would be devastatingly sexy.
In this moment, however, with a cock and balls, based mostly off his but a touch smaller, nestled between her normal feminine hips, the rest of her body also unchanged, she is also devastatingly sexy. Really, he supposes, she would be, no matter what she changed and what she left the same.
No erection yet; she's clearly nervous about this. Performance issues and nerves are another thing they've talked about a little bit, and Vax repeats now what he's already said to her: "Don't worry if you fail to get it up tonight. We can take this in as many steps as you need."
Keyleth nods. "Feels a little heavy," she observes out loud. "I suppose men don't notice the weight, 'cause it's always there." Gingerly she reaches down and runs a finger down it. "It is sensitive, isn't it?" Vax can't quite stop the sharp inhale, which makes her look, and she actually grins. "Looks like yours is working fine."
That's now fully hard, and Vax finds himself reaching down and taking it in hand, suddenly needing the relief. Keyleth watches him do so, and he now knows how to spot the dilation in her eyes and the rising flush of her cheeks as that gets to her. Except now, he's got another sure sign to look at, as her cock stirs ever so slightly.
Hoping to encourage that further, Vax strokes himself, slowly and lightly, just enough to take the edge off the tight pull of his desire, and watches Keyleth stare, hears her moan a little, and sees her cock start to stand up properly, her hand on it also stroking-until she seems to realize what she's doing, stops, and pants, "Do you want to do it?"
"For starters," Vax says, and he takes a firm but gentle hold of her cock, getting a gasp out of her. He's always loved feeling a cock hardening in his hand, and this one's now doing so quite nicely.
After a minute of just running his hand up and down, up and down, he adds, "If it's just a handjob tonight, that's fine, but I also want to suck you off, show you just how good that feels. And I'm pretty sure I'd love how this would feel inside me."
If the moans coming out of Keyleth are any indication, she's liking the sound of all that. "Can I suck it?" he asks, leaning over to whisper the question in her ear, punctuate it with a little lick to the lobe. Her head bobs a yes, and she even scoots back a little on their bed, to give him more room to situate himself. They've got a bigger one now, though his lower legs still dangle off it.
He lowers his head slowly, wanting to give her time to gather both her feelings and her concentration together. It is a little odd, when he's staring down the head his own cock only slightly scaled down, but Keyleth has also talked about making it sensitive in the same places (at least as far as she knows), so at least he knows just what to do.
And it is really nice to get to suck a cock again, to just slide his mouth down until it's full, to just enjoy the heat and feel and taste of it, along with Keyleth's, "Oh, no wonder you love this so much," spending a long minute sucking with just the right amount of pressure, before pulling back to tease all the right places with his tongue, making Keyleth gasp and pant. To wrap one hand around the base, and the other around her scrotum to play with that, all nice and warm.
Underneath him, Vax can feel Keyleth's hips twitching as she squirms and tries not to buck up. He pulls away long enough to say, "You can move your hips just a little," before diving back down, taking as much of her cock as he easily can at once. Her cry is a little sharp, and for a moment, Vax thinks her concentration might break, but the cock in his mouth stays there, and it stays as he more carefully sinks further. She made it small enough it's not too hard to get the head into his throat, and once again she cries out, sounding a little broken this time, but her concentration holds.
It also holds as she tentatively pushes forward a little. Vax takes hold of her to help guide her, and after a couple of awkward moments they have a rhythm. He makes pleased noises through his nose, hopes Keyleth gets from them how much he's enjoying this, even tries to raise his eyes enough to see her face, but her head's too far tilted back.
With her legs pressed against his head and one of his hands now feeling her muscles on her side, Vax can tell when she's getting close. He's fantasized about this more than enough to have developed a plan for this part. He pulls back, once again cups the base of her cock with his hands and just uses his tongue, then loosens his grip as he gives the head one hard suck. That's it for Keyleth's concentration, then. For a moment his mouth and hands are around empty air.
Then he quickly moves forward to where Keyleth's typical, familiar parts are there waiting for him. They're a bit dry, but Vax can already smell that fixing itself, and when he was nearly drooling around her cock, his tongue is more than wet enough when it wraps himself around her clit. It doesn't take much to finish her off; a few seconds, and Keyleth groans, her limbs quivering around him.
He's painfully hard by now, of course, and the first thing Vax does is move to get a hand on himself, only for Keyleth to surge forward and pull him into a ferocious kiss, taking hold of his hands and pulling at them until he's on top of her. Vax goes with it, putting his hands on her instead, cupping and stroking her breasts and neck, ready as ever to work her up until she's fully wet and open.
Except that, much to his delight, she instead lurches up, rolls them over, and even pins his arms down. It's only recently she's gained enough confidence to sometimes take control in bed, and much as he's loved taking care of her and helping her find what she enjoys, it's good to sometimes be able to let go and be taken care of himself again. And he's pretty sure Keyleth is very much about to do that.
"I loved that," she whispers to him, in between kisses. "It felt really good, of course, but it also felt so intimate, and to feel what you feel...I want to do it again. Maybe next time I will get inside you." Vax moans just at the thought. Also that his cock is so close to Keyleth's folds that he can feel the heat coming off them, even as he hears her quickly murmur the charm as she flicks her hands to keep herself from getting pregnant.
"Or maybe," she adds, "next time we see Tary, we can ask him if he has an Alter Self coin to spare. You can find out what it's like for me, what you do to me, maybe even what I feel when I do this."
She takes him in slowly, so slowly Vax feels like he might die. When he's all the way in, she murmurs, "It can be a lot, you know. Sometimes it still takes me a moment. But the more I get of it, the stretch of it, and the heat, the more I want. It's like there's a place inside me that's craving it, that needs to be filled, and then you get so deep and it feels so good..."
And Vax knows just how deep and exactly what angle she likes it best at, and she can even guide him to it, now. She's loud when he hits it, louder than she usually gets when she's come already, and that's it for him, too, his entire body curling up with how hard he comes.
Keyleth presses another kiss to his mouth before she just sprawls down onto him, and she actually giggles. "Guess you like that idea?"
"I do," he says. "We can talk about in the future." She hums her agreement as they slide together into an proper cuddle.