Razorfen Downs Quests

Before Entering Instance

Go to the Cathedral in Stormwind and talk to Archbishop Benedictus to start Bring the Light

Outside Entrance to Instance

Talk to Myriam Moonsinger to start A Host of Evil

Inside the Instance

Go to the Murder Pens area of the Razorfen Downs and talk to Belnistrasz to start Scourge of the Downs, which leads to Extinguishing the Idol.