Gross ones, mostly. There's three classifications of them, but the most common are trolls, which used to be humans before they succumbed to the Illness. Just about the same size as their host but way more disgusting and dangerous.

[... She's not sure she wants to frighten the teacher with descriptions of them.]

They're all really dangerous, especially the least common giant -- which is a bunch of trolls put together, basically -- and it's my job to get rid of them.