Much of the stronger spells in his sphere include Elder tongue, spoken words strengthening magic much like it does here with academic spells. But they learned all kinds of approaches to the same thing. He hasn't tried to cast with that in mind. The most magic he stored up and used during this entire experience was to knock Geralt out when he was attacking Steve.

Istredd knows this is going to hurt and he tries his level best to stay still, but it's still more painful than he expected so he swears under his breath. He feels light-headed again, struggling with consciousness. He knows what Steve is doing, trying to distract him while he's doing this, keep him awake, so he grits his teeth and pushes through it.

"I don't know exactly, in my late eighties probably. I don't have a birthdate, I was taken to the Brotherhood young." They take mages when they first use their abilities. Istredd was an early bloomer in that regard, or he must have been. They didn't celebrate birthdays. He and Yennefer did privately, for hers. If he survives he'll be able to celebrate it with her here. He doesn't remember a family, if it ever existed.

"When we graduate, they do a ritual." Slightly different from what they did in here, but probably not that much, outside of it being (mostly) consensual. It's not as if they can really say no. "It changes your body permanently. You can modify how you look and then it locks. It stays that way for hundreds of years." Eventually it does start to wear, but it takes a long time before that happens.