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 accessing DQVC. You first learn about her in Quest 149, Intriguing mystery.
On her orders, the tree on Pluvi Isle, which once touched the sky, was burned to the ground. The Gortess was also constructed by her, as you are told by the Gortress Guerrilla number nine, Digby, on top of the Gortress tower