Within the Book of Revelation, The Harlot is known as "Babylon the Great, Mother of Prostitutes and Abominations of the Earth," or "Whore of Babylon" for short.
She appears as wearing a purple robe. The color purple was associated with the Roman Empire. Indeed the Harlot and her beast can be seen as an allegory of Rome, the Empire and the Emperor. The beast she rides has seven heads. In fact, Rome has seven hills, so the heads could reflect the ancient power of Rome, which traditionally was one of antiquity's most powerful empires. Alternatively, the heads of the beast could represent the seven great kingdoms of the ancient world and their rulers.
"The Fiend known as the 'Mother Harlot'. She rides on a beast that had seven heads and ten horns and carries a golden cup, filled with the abominations and the filth of her actions."
—Shin Megami Tensei III: Nocturne Compendium
Mother Harlot, also known as The Harlot, is one of the fiends that the Demi-fiend must face in the events of facing Lucifer's trial of retrieving the Candelabra.
After the defeat of Sakahagi and Girimekhala at Yoyogi Park, rumors regarding a 'Beautiful Woman' are heard among the residents of the Park. Should the Demi-fiend choose to travel to the north chamber of the western entrance, he will be intercepted by The Harlot and transported to another realm. Facing off against the Demi-fiend, she shows her surprise about him simply giving away the Yahirono Himorogi after fighting Sakahagi and Girimehkala for it. Upon expressing her thoughts about him seeming more aligned with chaos rather than creation, she calls upon her seven-headed beast, who in turn questions the Demi-fiend about his resolve to gain a true demon's heart, even if he will forever be bound in darkness. Regardless of his answer, he will have to fight against The Harlot and her beast. Defeating her grants one of the Candelabra the Demi-fiend must retrieve — the Candelabrum of Beauty.
Once he reaches level 69, the Demi-fiend can summon The Harlot in the Cathedral of Shadows after defeating her using a Deathstone and performing a fusion resulting in a Tyrant during Half-Kagutsuchi phase.
Mother Harlot appeared as the final boss for the hard mode of the Greatest Summit Decisive Battle event that was part of IMAGINE's 7th anniversary event and was fought on a battlefield resembling a heat-deformed helicopter pad of the TMG Building. She was encountered as a boss after clearing all ten floors of the Soul Prison instance and has a total of three forms in her boss battle. In her first form, she spawned alongside Anzu, Kingu, Ose, and Flauros. After defeat, her second form appeared alongside the Four Horsemen of the Apocalypse, Matador, Hell Biker, and Trumpeter. This form used the Gate of Babylon attack, which deals a fixed 999,999 damage to all enemies in range. Her final form spawned alongside Seth, Shiva, Vishnu, Beelzebub, Metatron, and Astaroth. As the other bosses were defeated, her resistances were greatly decreased.
After defeating her, players had a chance of obtaining her plug-in item. She can be fused in a triple fusion of Pale Rider, Trumpeter, and Hell Biker. As a player demon, she can learn the signature skill Cup of Babylon, which is an almighty affinity shot with a high chance of inflicting charm and confusion.
In the alternative Shinjuku Babel's Abyss Tower instance, she appears as one of the four bosses. The battleground for this fight reuses the elevator aesthetic from the seventh anniversary event. Unlike the original fight, she only appears alongside Trumpeter and does not have multiple forms.
"The Fiend known as the 'Whore of Babylon'. Riding a beast with seven heads and ten horns, she carries a golden cup of abominations, and the filth of her acts."
—Shin Megami Tensei: Strange Journey Compendium
Mother Harlot appears as an extra boss battle in Sector Eridanus that can be fought at the behest of the angels Aniel and Kazfiel by battling them in tandem with Law alignment. She has been captured by the angels, who wish to see her dead. The protagonist, at her defeat, can elect whether finish her and her dragons, let her leave or stand in place and see how her dragons kill her and die. In either case, the angels reward the protagonist with the Amanomi Sword, the most powerful sword in the game. After her defeat, she can be summoned by Special Fusion using the four Riders of the Apocalypse as fusion material.
Mother Harlot is faced in the New Game PlusChallenge Quest, Ishtar, Goddess of Harvest, unlocked only in the Chaos Path. Found northwest in the Ikebukuro Region, she is one of the demons whose soul originates from Ishtar. Minako obtains her soul upon Mother Harlot's defeat. Defeating Mother Harlot unlocks her as a Special fusion between Trumpeter, Orcus, Ishtar and Legion. She's the highest-leveled Fiend of the game (second only to Ancient of Days), and her fusion requires defeating all hidden Fiends save for Chemtrail, as Trumpeter requires the four Horsemen as fusion material, each Horseman save for White Rider uses the previous one as part of its own fusion, and White Rider's own fusion requires Matador.
Mother Harlot appears as a Persona of the Empress Arcana in Persona 3. While she is fusable at level 69 in Persona 3, she is bumped up to level 74 in Persona 3 FES. She can also be found during Shuffle Time in Monad and the final 7 floors of Empyrean.