If you have not seen this already it will help get more quests for your Loremaster Achievement.
This guy is somewhat hidden and has to be jumped too in Arathi Highlands.
Also, after jumping down into the water, 2 things...
1. Sully Balloo's Letter - swim straight down. If you look to the right side of the middle pillar (the south east side) you can see Sully at the bottom of the river, and the letter is near his hand.
2. The quest from the hidden dwarf is timed. Swim quickly to the cave west of Faldir's Cove that leads back to Arathi and take the Flight Path to SouthShore. The dwarf to turn in is in the basement of the inn under the kitchen.
The Green Hills of Azeroth
2 months ago