XV Episode 10
A massive structure that destroyed the Kazanari Estate as it expanded.
It bears the name of the tree that supports the world,
but its functions and true nature are unknown.
What started its operation was the successful fusion of the Kazanari server room that sprawled beneath the Kazanari Estate.
From the fact that the Lunar Ruins began signalling as in response to the rising of the tower,
it is theorized that they have some relation.
XV Episode 11
From the remnants of Enki's will, it was revealed that Yggdrasil's true form was that of a "planetary environmental remodeling device."
The Anunnaki chose the earth as a vast experimental facility,
for creating life, stimulating evolution, applying remodels, and, in the event that it was necessary, effecting its disposal.
The Anunnaki, attacking the impasse that had frozen development like seeds,
attempted to break through the future that had been closed,
and constructed the Yggdrasil System in order to learn the final form of life.
Far from being the single column rising from the ruins of the Kazanari estate at Kamakura,
the Yggdrasil System is currently being established by Shem-Ha all around the world.
With the Symphogears away, the structure of the world was being redesigned.