Minagi

Minagi (魅凪) is one of the Six Ancestors, of the Succubi bloodline. She is infamously known as the "Great Whore of Babylon" due to her immense sexual skill, notably the Great Barrier of Babylon that raises sexual excitement in human males to the extreme, and is the most hated monster by Goddess Ilias. She also created the Lilith Sisters.

Monster Girl Quest trilogy
While Minagi makes no appearance, her moniker is mentioned a few times in Chapter 3.

When Goddess Ilias assaults the entire world and assigns Black Alice to attack the Succubus Village, the leader of the attack sent there, Eva, erects a large barrier known as the Great Barrier of Babylon. According to Alice, the barrier is a prohibited art that sends human male's sexual excitement to maximum levels, causing them to ejaculate mindlessly from simply being touched or seeing a woman; the barrier then absorbs the semen and converts it to energy for the caster. Luka is mildly affected by the barrier due to his immense strength and the sheer difficulty of reproducing such an ancient art. However, even after Luka and Alice defeat Eva, the barrier remains in effect due to its self-sustaining properly; it is only dispelled when Amira and her Unfortunate Friends snap the men out of their trance and stop fueling the barrier.

Lilith & Lilim are surprised about seeing the Great Barrier of Babylon in their era, created by the legendary Great Whore of Babylon. They comment that while they are considered legendary succubi themselves, they are not in the mythological class and may have been confused with the Great Whore of Babylon.

Monster Girl Quest: Succubus's Fantasy
Following the defeat of Goddess Ilias, Minagi somehow escapes her seal. Having come to a desire for Luka, the hero who saved the world, Minagi plots to turn him into her sex puppet. She dispatches her subordinate succubi to attack a remote village, successfully luring in Luka and his traveling companion and wife Alice, then transports them to a dimensional space dubbed the "world of temptation." Alice is distracted by illusions of parfait and disappears, while Luka is raped by illusions of succubi, Erubetie, Alma Elma, Crab Girl, Spider Princess, Emily, and Alice.

Realizing Luka's sanity hasn't broken despite constantly being pushed to the brink of death and being raped by an illusion of his lover, as expected of the hero who defeated Goddess Ilias, Minagi personally steps in. After a brief introduction, Minagi easily overpowers Luka and proceeds to rape him, but on the verge of death he finds the strength to retaliate and slashes her with the Angel Halo, dispelling her world of temptation. Luka wakes up in the real world and finds the real Alice looking over him, explaining that he passed out in the middle of the battle and ejaculated repeatedly in his sleep. Meanwhile, Minagi comes to desire Luka even more than ever, and tells him to be ready for the next party.

Monster Girl Quest: Paradox
Minagi makes no appearance in the first two chapters of Paradox, but is referenced by several characters.

One of Morrigan's lines when you talk to her in combat implies that, like Alma Elma, Minagi is a master of martial arts in addition to sexual arts.

During the battle in Grangold Castle, when the alternate Tamamo no Mae orders Lilith to handle the party, the latter tells the former that the Lilith Sisters are direct subordinates of Minagi.

Trivia

 * In Monster Girl Quest: Succubus's Fantasy, Luka should not have been able to retaliate against Minagi due to the effects of Critical Ecstasy. This phenomenon is likely a result of the whole event taking place within a dream world meaning Luka's willpower would trump physical laws.