Kill 8 Sprite Darters or Sprite Dragons. Use the Muisek Vessel to shrink and capture the fallen Faerie Dragons.
You should be able to get a Muisek from any of the faerie dragons in Feralas. After you kill them, target the corpse and right-click on the [Faerie Dragon 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 faerie dragons.
Faerie dragons can be found in concentrated amounts by the Grimtotem Compound west of Camp Mojache.
<name>, next I must have you capture a creature that in appearance, may look quite fragile, yet its powerful spirit is what we are truly after. The faerie dragons that I speak of have served the night elves as their allies. We must capture one so that the horde may benefit from this strength of spirit as well.
Here is the muisek, <name>. Kill 8 sprite darters or sprite dragons, and capture their muisek. They may be found to the west of here.
Were you able to capture the muisek of the faerie dragons?
Thank you, <name>. Now the spiritual powers of the faerie dragon will be available to us.
I hope you willing to perform another task for me.
- Breadcrumbs:  The Wilds of Feralas,  Hero's Call: Feralas!, or  Warchief's Command: Feralas!
- Welcome to Dreamer's Rest / Camp Ataya
-  Signs of Change
-  More Than Illness
-  Tears of Stone,  The Land, Corrupted
-  Sealing the Dream
-  General Shandris Feathermoon /  To Stonemaul Hold
- Feathermoon Stronghold (Alliance side quests)
-  The Battle of Sardor
-  Hatecrest Forces,  General Skessesh
- Breadcrumb:  Report to Silvia
- The Dire Maul threat: Tower of Estulan / Stonemaul Hold
-  The Gordunni Threat
- Side Chain:
-  The Gordunni Orb
-  Estulan's Examination /  Talk to Swar'jan
-  Ogre Abduction
-  Gordok Guards,  Rulers of Dire Maul
- Forces of Nature Part 1 / Weapons of Spirit Part 1:
-  Forces of Nature: Wisps /  Testing the Vessel
-  Forces of Nature: Hippogryphs /  Hippogryph Muisek
-  Forces of Nature: Treants /  The Flow of Muisek
-  Tell Silvia
-  Might of the Sentinels /  Might of the Stonemaul
-  To Camp Mojache
-  The Lost Apprentice /  The Darkmist Ruins
-  The Darkmist Legacy,  Ancient Suffering
-  Verinias the Twisted
-  Return to Vestia /  Return to Sage Palerunner
-  Adella's Covert Camp
-  War on the Woodpaw
- Horde-only side chain
-  Woodpaw Investigation
-  The Battle Plans
-  Alpha Strike
- Forces of Nature / Weapons of Spirit Part 2:
-  Treant Muisek
-  Forces of Nature: Faerie Dragons /  Faerie Dragon Muisek
-  Forces of Nature: Mountain Giants /  Mountain Giant Muisek
-  Weapons of Spirit
-  Stinglasher,  Zukk'ash Infestation
-  Sasquatch Sighting
-  It's Not "Ogre" Yet,  The Hilltop Threat
-  Taming The Tamers
-  Spiteful Sisters,  Twisted Sisters
-  Ysondre's Call
-  Taerar's Fall
-  Ysondre's Farewell