Colonel Flagg Gilgister was a Human hailing from East Terra (known as The East) and given his actions and appearance, it is highly likely he fills some sort of major military role. Flagg served the Lagoon Empire Army of the East and worn a Navajo white, military-style buttoned coat and cap, and has a large orange mustache. (In some artwork and scenes, he is seen fingering his mustache, making him something of an archetypal "mustache-twirling" villain.)
Flagg was a greedy, power-hungry man, as evidenced by his numerous laments regarding the cost of reviving the Dark Genie. He is also cruel and callous, as he throws away his assistant with no hesitation to the Genie's empty stomach, and wreaks havoc across The West by destroying several towns.
Some time before the events of the game, he acquired the urn in which the Dark Genie was sealed, hoping to be able to control its power. By mixing the blood of witches with humans (Curse Dancers, whom he had hired), as Seda had done 400 years ago to create the genie, he was able to break the seal. Riding off on the Genie, Flagg commandeers its power to wreak havoc across the West. The exact reason for this is unknown, though perhaps it is intended as a test of the Genie's power. He appears infrequently following the destruction of Toan's village. He is briefly seen in Dark Heaven Castle along with the Genie as Toan speaks to the Fortune Teller in Queens.
He is later seen again during the Sun Giant's mission briefing in Yellow Drops. During the battle against the Sun Giant, Flagg can be seen with red eyes, a sign that he is possessed by the Genie. After the Fake Genie is killed, the real Genie enters Flagg's body and reveals that he is the true Dark Genie. Due to his frail, human body, Flagg is unable to sustain the Genie's power and is killed once the Genie leaves exits his body.