What Npc Augustin mean by ethereal items?

Question

Hello,

I was selling loot today and I went to Bounac to Npc Augustin. While typing "Hi" NPC said  "Welcome, Hero of Bounac! Feel free to trade to your heart's content! I also buy several ETHEREAL and gnomish items."

What kind of items are they?

While typing "ethereal" NPC Augustin said: "Looks like you're not quite there yet, sorry."

Answer 1

He talk about Demonic Essence which can be sold to him only after meeting the requirements for sale in the "original" quest, i.e. after giving 3k of essence to npc (The Bone Master or The Dream Master)