Go to the Howling Vale and study the Tome of Mel'Thandris, then return to Sentinel Melyria Frostshadow at Forest Song.
Though we have put many resources and much effort into driving the remaining demons from the Felwood to the north, our successes have been few. We have been able to keep much of the demonic presence from Ashenvale.
To the north, near the Felwood border, the ruined shrine of Mel'Thandris has been overtaken by mysterious wolf-men. Their chilling calls have led the area to be known as the Howling Vale. The Tome of Mel'Thandris kept at the shrine may shed some light on why these wolf-men have come.