It's a runestone. That is supposed to freeze things temporarily.

[She says it offhandedly because of course she has to correct him, but Simidele has even tucked his large wings into his body to make himself seem smaller. Oh, he knows she is not pleased.]

And if you used too much energy, it could have turned you into a popsicle.

[Oh. Simidele didn't realize it could do that...but, well it didn't.]

But he seemed interested in knowing how they work! You could tell him about it!

[Sorry if he's talking about you like you're not standing right there.]