You will find Nilthiri just east of the Troll mound. Defeat her and the Spirit of the Grove will reappear and thank you what you have done.
Rest in the Grove a few days later and the Spirit of the Grove will appear again. It will ask to rescue Loren, a descendant of Marek who founded the grove.
Go to Trademeet and speak to Loren outside the town in the southeast corner. Encourage him to challenge the voices in his head and don't leave him. Chaos will appear and attack you. Once you have defeated Chaos, the Spirit of the Grove will appear again and thanks you for your service. It will give you the Golden Lion Figurine.
Once you have reached level 14, a druid will appear and tell you that you must challenge to become a Great Druid.
Speak to Master Verthan in the Druid Grove and accept the challenge. Defeat the druid and you will become the Great Druid.