Curiousity compels you to ascent the Wizard's Sanctum and speak with him. It turns out that Morganth, another mage, was corrupted by his studies of the dark arts. When he was banished, he took a powerful book with him. The mages of stormwind want that book back.
The high sorceror is quite pleased that Morganth was unable to overcome the wards on the book, and wants to reward you. He sets you off to the forests of Duskwood, to retrieve pristine spider silk suitable for an enchanted robe.
Some time later, with numerous half-healed spider bites, you take the silk to Wynne Larson at larson Clothiers in Stormwind. While you wait, she fashions the silk into a fine robe (or perhaps blouse).
Xavian, it turns out, has satyrs inhabiting it now, and they don't much like intruders. Still, you manage to slip in, grab a sample of their water from the pool at the bottom of a waterfall, and slip back out without a great deal of difficulty.
- Note: the waterfall you sought was the northerly one of a pair. [76, 41]
You return with the flask of water, and Deino keeps his end of the bargain. However, first you need to go get the materials for the robe. (Didn't think it would be easy, now, did you?) Your new robe is to be made of dryad hair from the Laughing Sisters near Raynewood Retreat in Ashenvale.