If that is "The World Tree," we have a few considerations from Norse mythology to look at here. It's the resting place of a few pretty nasty creatures or in FF world "HNM's." Nidhogg resting at its roots, which he also feeds from the roots as well, in the upper most part of the tree. We have "the Golden Cock (Serpent bird)," "Valefor." So I think its the resting place for Bahamut making the World tree a labyrinth of its own accord, just trying to get to the top to fight the Dragon God.