After defeating Feldorn in the Druid Grove, pick up your belongings and then talk to the challenge master and then rest. The spirit of the grove should introduce herself and ask you to perform a mission for the grove. She asks you to kill a troll shaman to the east of the troll mound (the shaman appears on the narrow path near where the spiders where on your first trip into the grove). She will give you the Root of the Problem to use although the Flail of Ages works great as well.

When you kill the troll, the spirit will appear and give you a Staff of Thunder and Lightning or a Cleric's Staff +3 (whichever one you don't get should be on the challenge master after you take over the grove and earn the Great Druid title). After 8 days, you should return to the grove and rest within the inner grove where you fought Feldorn to receive the second mission. The spirit will ask you to find a boy named Loren in Trademeet and to fight the evil spirits to rescue him. He is outside of the yellow tent along the bottom of the map. Just talk to him and tell him to fight the voices and to get him to release them to fight you. A beholder-looking beast named Chaos will appear and once you kill it {105-122 Hit points and worth 12000 experience points} then the spirit will tell you that you are done for now and will give you the Golden Lion Figurine and she teleports the boy to the grove.

Other than the items, you will only receive a small amount of experience points for killing the creatures.