Jabir is the true villain and final boss from Ys V, though he never appears until near the end of the game.
An alchemist from Kefin, Jabir found the Philosopher's Stone, which contained unimaginable power, deciding to take over the world. He took control over Kefin and started his plans to conquer the world, but he was stopped when other alchemists, who sealed him along with the entire city of Kefin within a time rift. In order to keep the city afloat, he used the Philosopher's Stone, commanding sacrificial rituals to fuel the stone.
500 years later, the seal weakened, so Jabir sent Rizze, the last descendant of Kefin's royal family, to seek the crystals necessary to break the seal. Rizze manages to break the seal and return to Kefin, but she is followed by Adol, who confronts them when they attempt to use the stone to restore Kefin. Jabir then fuses with the stone and morphs into a monster to confront Adol, but he is ultimately defeated and the stone destroyed, which causes the entire city of Kefin to disappear.
Ys Origin and Ancient Ys Vanished