Stellestria was once the combination of Celestria and Stella. She was an evil queen that caused chaos and suffering throughout the land. She is the subject of many quests important to the post story. The quests that involve her are gotten only by accesimg DQVC. You first learn about her in Quest 149, Intreeguing mystery.
On her orders, the tree on Pluvi Isle, which once touched the sky, was burned to the ground.