Since you have proven that you are both trustworthy and gifted with the ability to use the muisek vessel, I now wish you to capture another creature.
Hippogryphs have been loyal companions to the night elves for many years; their spirits are loyal and steadfast.
Your task is to kill 10 Frayfeather hippogryphs, and quickly, shrink and capture them with the vessel, so that their muisek may be preserved. You will find the hippogryphs in the High Wilderness, to the south of here.
Details
You should be able to get a Muisek from any of the hippogryphs in Feralas. After you kill them, target the corpse and right-click on the Hippogryph Muisek Vessel in your inventory. Make sure you loot the corpse first because it will disappear once the vessel is used. There is a short cooldown on the vessel, so you it is recommended that you use it as you go rather than waiting until slaying multiple hippogryphs.
The hippogryphs also drop quest items for the Natural Materials quest.