Geologist Larksbane at Cenarion Hold in Silithus wants you to recover the Crystal Unlocking Mechanism from the Qiraji Emissary.
You have been instructed to take the Glyphs of Calling to the Bones of Grakkarond, south of Cenarion Hold, and draw them in the sand. Should the Qiraji Emissary appear, slay it and recover the Crystal Unlocking Mechanism. Return to Geologist Larksbane if you succeed.
The glyphs illustrate an emissary of the Qiraji meeting with three silithid at the bones of a large dragon. Above the glyphs is what I can only assume to be a code of some sort. This code might very well be the key to summoning the emissary.
I will create a copy of the glyph code that you must use in the sand at the Bones of Grakkarond. If I am right, the Overlords will come thinking that new data is ready for transmission. Strike them down and confront the emissary. He holds the key to the crystals...