In Wilds North
The town of Snowhill is in the north of Sacred Grove, above the snow line. In the northern mountains is a Crystal Barrier that prevents further exploration at this time.
This quest is given by Scarlet Shadeveil in Snowhill, and can sometimes be tricky, especially if you forget or miss the hints! Here's a refresher on the hints for each step.
Still stumped? The answers can be found here.