If he’s honest with himself it takes him an embarrassingly long time to even notice.
When he finally does he panics quietly (really, it’s the only thing he does quietly), and rushes to Oxenfurt to bury himself in the library.
Geralt and Ciri come to pick him months later and he’s no wiser than he started, not really.
But evidently he has plenty of time so he puts it out his mind and goes wandering with his Witcher and the Princess once more.
His sister meets him at the door and something in him goes cold, freezes with fear.
Her hair is more grey than brown, her face and hands are wrinkled, she squints at him like she can’t see him clearly.
He makes it through the visit without incident and leaves a week later with a smile and a wave.
He could ask Yennefer. If she doesn’t already know she can probably find out.
For many reasons, he does not want to ask Yennefer.
“I think I might be immortal,” is not what he means to say when Triss opens the door but. Well, it’s not the first time his mouth has run away from him and it likely won’t be the last. “Apologies,” he says. “I meant to ask for your help in discovering why I don’t appear to be aging.”
She lets him in.
He accepts the cup of tea she offers him and they both get comfortable. “I really do apologize,” he says eventually, “for showing up unannounced like that.”
Triss waves a hand dismissively. “Don’t worry about it. You have me very curious, though. Will you explain?”
“Yeah,” he sighs, “I don’t actually know much. Only, I’ve been traveling with Geralt for almost thirty years now, and I was already in my twenties when I met him. I’m reasonably certain it’s not hereditary, because my sister is aging quite normally. And whatever else can be said about my parents, they were faithful to one another.”
“I see.” She sips at her tea, watching him over the rim of the cup. “And you can’t think of anything else that might explain this?”
“No.” He shakes his head. “Absolutely nothing. I think I’d be less worried if I had any idea why it’s happening.”
“Understandable,” she says. She sets down her cup and gets up. “I’ll need to examine you and then we’ll figure out what to do from there. You needn’t do anything. Just stay there and try not to move.”
He sets down his own cup, nods, and settles in to wait.
Triss takes his right hand and puts her other hand on his cheek, closes her eyes and stills.
He’s still a bit dazed when he meets up with Geralt and Ciri.
Geralt eyes him suspiciously until Ciri starts talking to Jaskier and he responds as usual.
Still, the first time they’re alone together, getting ready for bed in an inn, Ciri down the hall, Geralt interrupts his nighttime routine by taking his hands and pulling him close.
Jaskier closes his eyes and lets himself be held.
After some time Geralt says, “Did something happen while we were apart?”
“I went to see Triss Merigold,” Jaskier tells him without moving. “She told me that, at some point in the last thirty years, someone gave me a blessing. Eternal youth. I’ll never age. Haven’t for some time.”
Geralt hums. It vibrates through his chest into Jaskier’s. It’s acknowledgment and question in one.
“Not a bad thing exactly. She says it’s unconditional which is apparently very rare indeed. I’m just a little worried because she said it’s not the sort of thing one can do without direct contact, and I don’t remember it happening. We think it must have happened when I was between twenty six and thirty but she couldn’t even be sure when.”
Geralt hums again. “You used to drink a great deal then. You didn’t always remember the next morning.”
Jaskier huffs out a laugh and holds on tighter. Geralt follows suit.
“Come on,” Geralt says, “time for bed.”
Jaskier lifts his head to grin at him. “Oh my. Are you propositioning me?”
Geralt rolls his eyes but leans in to kiss him.
(He’s twenty-seven and still high on a performance gone incredibly well and astonishingly, impressively drunk and when the stranger offers him eternal youth if he can win at some dice game Jaskier doesn’t actually know the rules to, of course he agrees.)