You receive this quest from Michele_L who is in the Boardroom of Gods.
She says to reach the fortress that Coventina is being held prisoner in, you'll need to climb the cliffs.
The fairies will help you if the you circle their mound of mushrooms near the cliffs correctly.
She also says to climb higher to the fortress where Coventinas being held, you'll need a special Knotted Rope.
You can get the Knotted Rope from the Tree master in Old Shamans Forest.
You will receive the Circle the Mound quest.
Go to Old Shamans Forest, which is on the Western part of the Island.
Touch the Northern statue.
It will give you the Cloak of Invisibility so that you can get to the tree master without him teleporting away.
I don't know if you need to complete the Relieve Boredom for the Northern Statue to give you the Cloak of Invisibility. So if the Northern statue doesn't give it to you, complete that quest first then it should.
Equip the Cloak Invisibility and go talk to the Tree Master.
Talk to the statue in the middle and you will be rewarded with 3 knotted ropes for getting hold of the tree master.