Ouroboros (Bravely Default)

Ouroboros is the main antagonist of Bravely Default, and acts as the final boss of the game. It is he who sends Airy on her quest to awaken the crystals in multiple worlds to felicitate his ascension.

Story
Uroboros is a deity in the universe of Bravely Default, wishing to destroy all realities and reach the Celestial Realm, wishing to invade and conquer it. In order to accomplish this, he uses his servant Airy to travel to the multiple versions of Luxendarc and overstimulate the crystals, causing them to create common links through all realities and enable Uroboros to reawaken. To this end, Airy tricks and expliots multiple version of Agnès Oblige, Tiz Arrior, Edea Lee and Ringabell. However, the first version of Agnès managed to send out a warning through the Celestial Realm, which eventually reached the four's latest versions. The four go on to defeat Airy, and then Uroboros himself.

Etymology
The Ouroboros, which stands for "tail-eating snake", is a symbol found in several European and near-Eastern. The symbol is of a serpentine creature eating its own tail, forming a circle. It is often interpreted as symbolizing the cycle of life and death, and reincarnation.