The Tree of Souls was a sapling planted on the newly formed Evermeet by the elven gods Angharradh and Corellon Larethian and given into the protection of the high mage Starleaf after the completion of the magic which created Evermeet in The Sundering. 
The Tree of Souls remained in Evermeet and in the protection of the elves there but, after the failed conquest by Kymil Nimesin, the Queen, Amlaruil Moonflower, gave her son, Lamruil Moonflower, a bud of the tree. The Queen imparted to Lamruil that the time to plant the Tree on the mainland had come.
Lamruil took the seed, and traveled to the most northern reaches of Faerûn, and there established the elven settlement of Auseriel. There he planted the tree, creating a haven for elves on the mainland.
In 1373 DR, Auseriel was abandoned and Lamruil retreated with the Tree to Evermeet to prevent its destruction. The tree was returned to Queen Amlaruil for safe keeping. In 1377 DR, Amlaruil brought the Tree back to the mainland and presented it to Ilsevele Miritar, seventh Coronal of the recently recaptured Myth Drannor.