A Different Approach is a Horde quest in Thousand Needles that involves finding and killing Earth Elementals and collecting [Purifying Earth] from them, in an effort to help find a new method for combating the Blood Elves' magical addiction.
It was introduced in patch 2.0.1, and the quest objective was reduced in 2.0.3 (4 handfuls of Purifying Earth to 2).
It’s simple. My brethren will no longer have me. Every copy of my treatise on natural cures for our magical addiction was burned.
I can safely pursue my research here, but I am without my reagents. If you’d be willing to gather purifying earth from the thundering boulderkin near the western end of the Needles and deliver it to my associate at Whitereach Post, I’d appreciate it.
Magistrix Elosai's note was a bit cryptic, but I think I understand what she wants me to do. If you have the earth she talked about, I can put it into the vessel you'll need for the moonwell water.
What? She didn't mention the moonwell? That's what she had in mind all along. I admit the whole thing's a bit wacky, but who am I to turn away a client, especially when she's the only one I've got?
Maybe trying to sneak into a night elf settlement and steal water from their moonwell isn't the most prudent thing I've ever helped a customer do, but her money is as gold as anyone else's!