- "I shall show you now what it means to command the powers of a god."
- —Ethereal Queen
The Ethereal Queen, also known as the Iselia Queen or Iseria Queen, (イセリア クイーン Iseria Kuīn) is a recurring hidden superboss from the Star Ocean and in several other tri-Ace games. A Celestial being, she is often the most powerful enemy in the games she appears in, with exception of Star Ocean: Till the End of Time, where Freya is the most powerful enemy, as well as possibly The Second Story/Evolution, in which some consider the unlimited version of Gabriel to be more difficult. She can only be fought after Gabriel Celeste is defeated, as his defeat is a prerequisite for her to be found.
In every game in which she appears, the Ethereal Queen has short conversations both before and after the battle. These talks reveal an egotistical personality born of her extremely powerful race. She usually views everyone else as inferior, arrogantly offering servant positions in some games (which result in the boss battle upon rejection). Upon her defeat, she often asks the question, "What will you do with the power you have?" This question has an ironic side to it, as the Ethereal Queen is (in many cases) the hardest boss in the game; upon beating her, there's nothing else to fight.
- Main article: Iseria Queen (Star Ocean 2)
Iseria Queen can be summoned by having a character with Music level 10 play "The Devil's Aria" which requires the Silver Trumpet. The Silver Trumpet can be obtained after defeating Gabriella Celesta in the lowermost level of the Maze of Tribulations. She is one of the most powerful bosses, second only to the Final Boss Gabriel/Indalecio when at full power.
Iseria Queen appears in the Cave of Trials, immediately after Gabriel Celeste's defeat. You can either fight her then and there (no healing or saving), or be warped outside to heal and save (but go through the dungeon again to fight her).
- Main article: Ethereal Queen (Star Ocean 3)
Ethereal Queen can be fought in floor 211 of Sphere 211, although Gabriel Celesta must be defeated first in the Maze of Tribulations in order to unlock the floors leading up to her. Once she's defeated, she hands over the orb to unlock the final bonus boss, Freya. The player can refight her each time they return to floor 211. A special feature to take note of is that this boss has two different arenas she can be fought in. One inside of a cathedral while the other appears to be a see-through platform hovering over an endless world of gold fields with the sun setting in the background
- Main article: Ethereal Queen (Star Ocean 4)
The Ethereal Queen resides in B20 of the Wandering Dungeon, reappearing every second floor beyond that*. She grows more powerful each time the player defeats her, sprouting four, then six wings to indicate this. She hands over an Ethereal Queen's Feather each time she's defeated. When defeated the first time, the player can receive Recipe Memo 04.
After defeating her, the party returns to B18 and has to complete the floors again before fighting her again.
The Ethereal Queen is found in the Maze of Tribulations bonus dungeon. Similar to in SO4, she has 3 iterations, each more powerful and with more wings, which are the ultimate test of your power. When defeated, she drops a Matriarch's Feather, regardless of which iteration is beaten.
Ethereal Queen is a superboss found in a post-game dungeon called Seraphic Gate,as in other games of tri-Ace, you must defeat Gabriel Celeste before reaching her.
Iseria Queen is found at the end of the Seraphic Gate, after Lenneth defeats Gabriel Celesta.
The Ethereal Queen is found at the bottom of the Seraphic Gate. Much like in Star Ocean: The Last Hope, her stats grow stronger after each defeat.
Ethereal Queen appears as the final superboss at the end of the Dragon God Dungeon.