Thal'darah Grove is a Druid training ground located between Thal'darah Overlook and Farwatcher's Glen in Stonetalon Mountains. It plays a key role in a quest chain involving the bomb. The quest ends when the bomb is dropped on Thal'darah Grove ultimately destroying it. It should be noted that unlike other phasing content which is mostly hidden, this phasing content happens in real-time. You will see the bomb dropping on Thal'darah Grove and its subsequent destruction.