Estaven

More commonly known as "The Fucklord".

Probably the most repressive Incubus King, with the most unusual harem (except possibly the Doom King). Every girl "belongs" to him and all people in Erosia can't find sexual relief unless it is with him.

Now that you have met him, Riala's words about "that guy from Erosia" make more sense.

He wears a fedora, or possibly a trilby, and in many ways fits the negative stereotype of one who does so. He is distractable, vain, and insecure, even to the point of having less sex than one might expect an Incubus King to. If he has any positive traits, it is those the harem scholar hints at: He's smarter than he looks, powerful, and driven when something catches his interest.

His inner harem has one of each of a "type" of girl that he likes, chosen solely for that reason. (Yarra expresses approval of the concept, if not the execution.) Most have a sort of anime flavor, Erosia being the vaguely Asian culture of the setting. They include: They despise him, and are able to say so because the Fucklord only cares that women obey and "belong to" him, not that they like him. They are also forbidden to come without him, even though he rarely fucks them, and laying with anyone else makes them sick.
 * a ninja
 * a child
 * a scholar with glasses, chosen because shy and glasses
 * a very decorated geisha or something
 * a girl in a playboy bunny outfit, who doesn't know much about the outfit but is just glad her sister wasn't taken instead
 * a "MILF" taken from her husband
 * an excitable girl whose ability to emote sadness has been destroyed
 * an Aramite former mage, whom the Fucklord gave meaningless markings because she looked exotic
 * separate from the others, a mysterious woman with pointed ears who refuses to say what race she is but calls others "mammals"

Story
The Fucklord organizes the Succubus Hunt event at the Gathering, leading to Yarra and Qum nearly being claimed as property of The Incubus King. Yarra's show of resistance to this nearly earns her a vendetta, but ironically The Fucklord's (off-screen) squabbles over who won the event serve to distract him, inadvertently protecting Yarra.

Trivia

 * His Incubus King title is derived from the original name of the game "The Last Fucklord". HIs ridiculous nature is also a reference to how the title is unfitting to the more serious nature of the game.