Speak with Slate Quicksand at Needlerock Chasm in Deepholm.
Down below in Needlerock Chasm is where the mystics are sprouting all of these fungal monstrosities. I sent Slate Quicksand and a small force to deal with it, but they've run into a snag.
You remember the Arch Geomancer? Would you fly down there to the northeast and lend him a hand?