This quest is not available in game.
Return to Darnassus and speak with Mathrengyl Bearwalker in the Cenarion Enclave.
The time has come for us to part ways, young one, as the application of your lessons takes you back to whom that sent you to me. Mathrengyl Bearwalker walks truly in balance with nature, even as he dwells precariously close to where the balance has faltered. Listen to his instructions, and you will soon complete your first lessons into your role as a protector of balance.
Go now, young one. We shall meet again.