World Tree

The World Tree was a sentient tree-like cosmic structure in the World Tree cosmology model that connected all of the Celestial planes to each other.

Cosmography
The World Tree's roots were located in Dwarfhome and Arvandor, its lower branches in Green Fields, the House of the Triad and Dweomerheart, its main trunk along the House of Knowledge, Golden Hills and Brightwater, and at the top were the Gates of the Moon.

Normal planar travel used the Astral plane to pass from the Prime Material Plane to one of the other Outer planes and all inter-planar journeys had to pass through the Prime Material nexus. Angelic servants of the good deities used the tree as a kind of "celestial ladder" to avoid having to go through the Prime Material plane, although the tree did not enjoy being used as such.

Inhabitants
Mortal travelers would often meet celestial treants and dryads sent to prevent their passage. However, if their intentions were noble enough the tree usually allowed them to pass unhindered.

History
The World Tree was destroyed in by the Spellplague.