Key: First report to Farmer Hugh - then go to the blue Boar Inn/cellar

Elven treasure: The sacred elven items? Yes, they're were Josie is.

Necklace: Dwarven Halls jeweller, speak to him - but why do you have this quest??? You haven't solved the war between elves and dwarves???

Feign potion: Go to the church/Rivertown area, Father Teophilus has it in a speech option

Plague prob: Look into the poor quarter: main gate with cut scene and then side entrance in the west to get in, have a close look in there

Tingalf: It's a spoiler, but this quest is easy to break, look at my post there, click please
Kiya