The World Tree is a gigantic living Atlas as well as a chart in and of itself. The nodes used to travel between charts are on its exterior, where it is eternally night. On the interior of the World Tree, there are entire nearly-isolated ecosystems, complete with flora and fauna common to other worlds and unique to the World Tree. The tunnels between ecosystems and to the exterior of the World Tree at any one time are known only to Galactecles, the keeper of the World Tree, who has a soft spot for travelers who bring him cow's milk.
Fall of the World Tree
The World Tree is the final Atlas to be destroyed. A group of Denizens take it to the Manifold where they attempt the first completion. That is, they attempt to turn it into a native Manifold life form. They fail and resort to turning it to stone, preserving its exact structure until such time as they can restore it.