The Treeheart Chamber is a special Vault within the Alchemist's Grotto. It is the center of the Evertree, and this special chamber is where the Song of Myora once resided, before the Song was shattered and the Fragments scattered about Alaria. Once, long ago, the Aerum, especially the Everheart Alchemists would visit the chamber to commune with the Tree and the Song, but after the Song was shattered and The Withering took hold, no one could enter and the Chamber was lost.
The Everkin, guardians of the Tree's heart, were given the final fragment of the Song, to protect it until such time as hope had returned. That hope is in the form of the Apprentice, who must locate the missing fragments and place them all in the Treeheart Chamber.
The chamber itself is a very large, underground chamber, nestled among the roots of Evertree, while the heart of the Evertree hangs high above the platform where the Apprentice first arrives. The platform is made of white and grey stones, with a waterfall running amongst the low interior walls of the chamber. Eight pedestals are arranged about the platform, awaiting the placement of the Fragments of the shattered Song of Myora.
As the Apprentice collects Song Fragments, they must return to the Treeheart Chamber to place each on a pedestal. Doing so pushes back The Withering, and causes the Evertree to experience a sudden surge of growth (which has the side effect of unlocking additional Seed Planters for additional World Seeds). The Evertree will then speak to the Apprentice in the form of memories.