Istredd creates a telekinetic shield around himself instantly, moving a quick dash backwards from her. But he doesn't go farther than that, nor does he try to surprise or attack her. This is merely to keep from needing to dodge continued violence, and she will find that his shield is very difficult to get through. Stronger than many mages, considering where they are.

"I'll explain, just stop trying to threaten me!"

He thinks that is a perfectly reasonable request. Her reaction only gave him confirmation of what he suspected. It feels like he just went through an ice bath, like water crashed down over his head, metaphorically. Princess Cirilla is not only real, but she's here in front of him.

"Geralt approached me and said that he knew the monolith in Cintra was destroyed. He thought there were monsters inside of it. When we investigated, and we came to the conclusion that the monoliths were gateways, and suddenly we heard a girl's voice screaming Geralt's name. Everything shook, the monolith pieces rose and seemed to be sucked somewhere, and then a new monster appeared. One never seen before in our land. It flew away. Geralt asked me to teleport him away without answering questions."

No matter what Istredd asked, the witcher had no interest in answering, and once it all came together, Istredd understood why. The girl was under his protection, apparently, he had to go for her. And he probably suspected the monster knew where it was going.

"Afterward, I decided to look into how the Cintra monolith was destroyed the same night the castle fell. I followed a hunch into the royal bloodline, and that girl who called out to Geralt was identified as Princess Cirilla. Someone with the ability to affect the monoliths."

And might be therefore afraid of them and perhaps even her power over them.

"I am not after anything other than knowledge. I had no idea you were even here."