The World Tree is a colossal tree in Bossniri (formal name Bossnirivhonicanioklythorn), a region located in western Obreidhion in Khyorgan. A clan known as the Wood Elves tend to the tree are part of the Ythulian Monarchy.
According to legend, the tree once held up the great plane of Eidyn on its crown until it broke off, drifting away deep into the ether. However, this belief is supported mainly by Valkyrii legend, and conflicts with known history of both planes. Valkyrii legend is known to be an unreliable source of information. A more accepted belief is that the tree grew from a shard of the Aard'Vorn staff used by the Sentinels.
The tree has an extensive system of roots, which has carved an even more extensive system of caves. It was here the mysterious Root Carvers lived in the Creation Era and the beginning of the Magitek era before they disappeared.
During the War of Khyorgan, much of the tree was burned by Colossus Demons. Countless Wood Elves died in defence of the tree, and half of Khyorgan's High Elf population died in battle. The tree was saved, and despite having been reduced in size a great deal, it is still alive, though it's magical power was considerably weakened. Though wizards work constantly to help heal the ancient tree, what it requires is time.
Some legends and prophecies state that the tree will one day reach it's roots out towards Eidyn, and in their darkest respective hours the two realms will be united. This prophecy is supported by the Kronos Elves, so it probably has some degree of credibility.