With the blessed water, I was able to break the link between the flute and the ancient spirit. I do believe though, that if you were to use this flute in a sacred spot, you may be able to summon the ancient spirits.
Perhaps you might try the ruins in the southern part of Irontree Woods. Many corrupted treants inhabited this area at one time, and it is possible that they may still reside there, even in spirit form.
You will receive:
(or 4650 if completed at level 100)