A long time ago, another mage tried to summon people from other worlds. He was exiled for it and became the founder of Solvunn. Until Ambrose, they didn't try it again. Of course Istredd being Istredd, he was intrigued by the history of the kingdoms and it was the first thing he looked up.

She could have ordered him to, he's only been nine years in his position. Hard to say. But I'm not sure anyone is harmless. In our world, mages are placed in courts, specifically to try and manipulate the monarchies. Yennefer could probably tell him more about that than Istredd did. It's why she is so good at it herself, becoming close to the Queen.

His look is speculative and his humor evaporates. I hope you don't mean you, Lucifer. I'm not the coup-throwing type. For one, a Summoned would not become the next person in power, for two, Istredd can barely tolerate people now. He wouldn't want his best friend to be the leader out of no where. Or we could try to get the king to get it together and take the reins back. He seems more reasonable.

As for the heat joke, well, he scolds himself internally for nearly getting flustered over something so stupid. And pointless. I already went to a magic school. He doesn't get the reference! I can find you that enchantment.