Back in Balinhost, even though Saladin is given most of the attention, the gnolls are asked a lot of questions about the fey they encountered.
They bring in several experts to talk to you. First, two Fironi, and halfling, a human. They ask lots of questions mainly focused on types of fey, how they looked and such.
When one of the Fironi leaves along with the halfling, the two that remain ask more pointed questions about weaknesses and strengths.
You learn that the fey are an extremely difficult enemy, so says the human named Vernon. "They do not breed normally. Each one might be resistant to different things. You don't even know if you can kill it by drowning.". They laugh. "One fey really had us going when we were water boarding it for hours before it finally couldn't keep the joke up and laughed at us. It could breath water."
The Fironi cringes at the next part before it is said. "It couldn't breath fire though."
Note that only the gnolls, specifically Ozzie and Tarkin.