Ouroboros is a large dragon-like monstrosity with several tentacles protruding from his back. He has four arms, a large horn and a jewel on his face that serves as a regeneration system. He has several tails dangling below him in place of legs and a structure with orbs on the tips resembling the frilled neck of a jester. Most of his face is covered in shadow and featureless, except for two glowing white eyes.
Ouroboros is callous and self-centered, viewing even his most important and loyal servants as similar to cattle: A beast of burden to be devoured after they outlive their usefulness. He is arrogant and is indifferent towards most things, often finding joy in "amusing" things while disregarding those that are "boring". He claims he wants to bring destruction, corruption and several negative aspects into the Celestial Realm only because he finds its peaceful nature to be plain. Cruel and sadistic, he enjoys toying and tormenting his victims.
The Mark upon the Evil One heralds the beginning. The Bringer of Ruin has risen. His name is Ouroboros.
Ouroboros sends Airy on her quest to awaken the crystals in multiple worlds to facilitate his ascension. Ouroboros is a deity who desires to consume all realities and reach the Celestial Realm, planning to destroy it and create a reality in his image. His servant Airy travels to the multiple versions of Luxendarc and overstimulates the crystals, causing them to link all realities that would give Ouroboros passage: The Great Chasm. Airy tricks and exploits multiple versions of Agnès Oblige, Tiz Arrior and Edea Lee to achieve this.
A previous Agnès sent out a warning through the Celestial Realm, which reached Sage Yulyana and Lester DeRosso who established the Council of Six with the intent to stop Ouroboros, but not to harm those Airy is manipulating. The only one to know of the ancient founders' intent, Braev Lee, sees stopping the wind vestal by any means as the only way to ensure Ouroboros does not come. Joined by Ringabel, the latest version of the group learns of these truths after Airy decides not to kill them, and instead use them to link the five remaining worlds before departing to meet up with her master.
Intrigued by Airy's defeat when the group pursues her, Ouroboros devours her once she outlives her usefulness. Ouroboros is forced to assume the forms of Agnès and her party to interact with them and reveal his plans while sensing a Celestial within Tiz. Ouroboros drags the heroes into the Infernal Realm to fight them in his true form, displaying his ability to regenerate. Lester DeRosso arrives to enact his role in the demon's defeat by merging into Ouroboros's core to halt his regeneration. In the battle that follows, Ouroboros shows his ability to destroy and consume worlds that Airy already linked to force the group's unconditional surrender, lest their homeworld ends up being obliterated. The party enlists the aid of their other incarnations to disable the link before they defeat Ouroboros.
Ouroboros is the final boss, fought in a series of five battles. He is first faced while assuming Tiz's form. The next four battles feature his actual appearance. Each battle includes an increasing set of skills, and has different criteria for entering the next battle. Ouroboros can be killed in the fifth and final battle.
Ouroboros's theme is "The Dark Aurora", which is also the final dungeon theme and his penultimate boss theme. His final boss theme is "The Serpent That Devours the Horizon". A loop of the first half plays during the second and third battles, while parts of the second half are heard during the cutscenes between them, and during the fourth battle part of the second half is added. The full theme is played only during the fifth and last battle.
The second half samples many themes, such as "Land of Light and Shadow", the main characters' special themes and "Overture to Hope", the main theme. Interestingly, the first half sounds similar to Bizarro∙Sephiroth's battle theme, "Birth of a God".
Ouroboros is Greek for "tail-devourer". It is an ancient symbol depicting a serpent or dragon swallowing its own tail and forming a circle. It most commonly symbolizes cyclicality, unity, or infinity.The