Evolving, devouring, and nightmare ectoplasms drop the essences. It is a 100% drop rate.
Ok, so the raptor horns didn't work so well. But that's all right -- no one got rich on their first try! And besides, I think I found something that'll work even better in my smart drinks!
There is a substance called Wailing Essence, and I think it is the cause of the strange plants and animals in the Barrens. Get me some and I'll try it in my drink!
I heard the essence gathers in ectoplasmic creatures in the Wailing Caverns to the west. Hunt those creatures and gather the essence.
Where is my wailing essence?
Great, you got it! I can't wait to try it out. This is going to make me a fortune, I just know it!
Thank you, <name>. Take this, and after I'm rich I'll send you more, I promise!
-  Raptor Horns