"I do not know if Shalelu's in town - she reports to the mayor, not me. Though I'm sure the mayor would send for you when appropriate, and so far no one came here looking for you." - the sheriff then affirms that he had looked at the diary - "I would suggest we meet with the mayor today and send someone to Magnimar at first light tomorrow, with an official letter, the diary, and all. They might be able to send some help."

You find Brodert Quink and Chask Haladan both at The Curious Goblin, which is located along the Main Street right next to Turandarok Academy. Ilsoari Gandethus is at Turandarok Academy, which is part school, part orphanage, and while it has a classroom free for everyone to gather together, Chask prefers not to close his shop and offers instead to gather more tightly in the reading room of The Curious Goblin, especially since the shop has a wider selection of relevant books to refer to.

You describe the creatures you met down below and the strange pool of hate. You get full book entries on the quasit and the vargouille. The use of sleep and summoning of monsters by the quasit are noted as unusual, but quasits are intelligent, some more than others, and so can be taught.

Broder Quink is less certain in his statements. He says that thassilonian runelords were numbered seven. Each ruled over a nation, all of which were part of the ancient empire of Thassilon. Each preferred and heavily used a separate school of magic. The enraged woman, statue of which you have discovered, is most certainly runelord Alaznist, who ruled over the nation of Bakrakhan and controlled the domain of Wrath. The pool of hate is most likely a runewell, some sort of rechargeable accumulator of Wrath, and the strange unidentified creatures are sinspawn of Wrath. Broder cannot say much about them except that they are aberrations, somewhat resistant to magic, closely tied to the relevant sin and generally not encountered in modern Varissia.

Spoiler
Show
Brodert Quink does not have a shop, he has a house near the Old Light. The book shop is owned by Chask Haladan. Anyway, Brodert Quink's in the book shop, reading in one of the chairs there.

Chask Haladan profession (librarian): (1d20+13)[24]
Ilsoari Gandethus know (the planes): (1d20+17)[27] vs quasit
Ilsoari Gandethus know (the planes): (1d20+17)[31] vs vargouille
Brodert Quink know (dungeoneering): (1d20+17)[25] vs sinspawn
Brodert Quink know (history): (1d20+20)[24] vs the pool of hate
Brodert Quink know (history): (1d20+20)[27] vs runelords (and particularly Alaznist)
(the above includes bonuses for having access to books and knowledgeable people helping each other, but no inspiration)