Story
A collective effort is required in order to restore the altars one by one. Go to the Wind Altar first.
After completion (spoilers)
"If they had been lost, healing the Sacred Tree would have become entirely impossible." A collective effort is required in order to restore the altars one by one. The Wind Altar was the first stop. While restoring the altars, you and Nemon came across some Spirit Guides. They told you that they were trying to remove the Poison Blood from the Purifying Forest. You decided to restore the Fire Altar and meet another Spirit Guide.