Isildragg

Isildragg is the great stone obelisk that stands at the dead centre of the world, also known as the Tree of Life and Death. Is resembles a titanic oak with bark of stone and leaves of copper, and contains sap which is the metal silver. Isildragg was created by the intermingling of Nito , the Underworld with Orboros , the earth and soil above it, and its existence substantiates the linkage between the cycles of Life and Death. Legend states that should the Tree ever be destroyed, that life and death would be disconnected and that the world would be thrown into unimaginable chaos. For this reason, numerous attempts by the forces of Darkness have been made to do just this in the cause of Annihilation .
Beneath the roots of  the Tree, the vast warrens and cave networks inhabited by the chthons and their nidhogg overlords serve as a bastion against attacks from the Underworld itself, while within the main trunk of the Tree exists the greatest temple to Tey'Kor-Akx within the world, where the greatest and most powerful of the oracles watch over Time itself. Due to its location upon a small island standing in the centre of the Central Sea, a substantial attack made upon the Tree on the surface is nigh-impossible. for this reason, most attempts made to defile  the tree have been made form the air by great dragons serving Oblivion.