So we find key from guy we de-stoned in order to get into library. We wander around ground floor, and creepy voice from nowhere keep warning us to get out because library closed. We ignore it and things start getting weird. Eventually books fly off shelves and form giant book monster, but we manage to beat it. 

We don't face any trouble after that. We go up stairs and find a locked room with Mendor's burned corpse. Apparently he looking for info on Tyranthaxis, and it get him killed. We find four books hidden in magic sack that seem to have to info on him. 

So with library clear, we go back to council to tell we get into library and take out monsters guarding it. We also give them some books they looking for (but not secret books we found).