Deep in the mountains, under a large spreading tree, lies an ancient elven city. The elves protected and cared for the World Tree, because it was the source of their power. But in those ancient times, war broke out. Invaders from other worlds came to the world of the elves and wanted to seize their power. The elves fought with all their might, but could not defeat them, and then they decided to use the full power of the World Tree. The tree released all its powers, destroying everyone around, including the elves, and itself died. Many millennia have passed, and only the majestic ruins of the ancient city lie lonely under a dried tree, reminiscent of the great feat of the former civilization.
https://www.artstation.com/artwork/49vDWn