There's also this.

[Nadine pulls out one of the withered flowers Hilda had given her to inspect and lays it on the table.]

This was found at one of the sites where a Summoned was taken. I don't know exactly what happened to it, but it wasn't natural. This happened quick. But I'm not a skilled mage and I'm only an herbalist. Someone with more knowledge or abilities may be able to tell more.