Mamono Lord

The Demon Lord, alternatively translated Monster Lord or sometimes Maou, is the leader of all the monsters in the Monster Girl Encyclopedia world. There have been multiple Demon Lords, and the title may have been held by very many monsters since the creation of the world. Previous holders have been bloodthirsty anthrocidal killers in the classical "monster" tradition, but the current incumbent, a succubus, is rather more a lover than a fighter.

The Current Demon Lord
The current Demon Lord is responsible for transforming monsters into the human-loving creatures we know of today, and is the mother of all the lilim. Other details on her personality and interests (beyond sex) are sketchy, in spite of her central role in the Monster Girl Encyclopedia. She is at least mentioned to deeply love her husband, and the human species in general. One tidbit about her other hobbies is that she is an accomplished Magic Gems crafter. Also, the story on the punishment of the Tentacle Forest probably relates to an adventure she personally embarked on early in her reign (although the "white-haired succubus" to which it refers could conceivably be one of her daughters instead).

Although all monsters would agree that the Demon Lord is, at least in a nebulous sense, their "leader", the degree of control she exerts over different factions and species varies considerably. For example, while the monsters of Zipangu appreciate and respect her for giving them female forms, they are in practice almost completly autonomous. Nevertheless, the Demon Lord's metaphysical sovereignty over the monsters does affect their behaviour: just as her succubus nature influences their bodies, so too her personality influences their minds, giving all most monsters a preference for monogamous relationships and not stealing other girl's husbands.

Usually, Demon Lords come to power over many years by butchering their way to the top of the pile of slavering inhuman monstrosities, with (allegedly) the tacit approval of the Chief God, having perceived that the human population needs thinning out a bit. For reasons unknown, the present Demon Lord was able to short-circuit this process, gaining the title by acclamation from the other monsters. While most monsters in former ages literally ate humans for breakfast, the Demon Lord was instead motivated by a deep love of those creatures that were supposed to be her enemy (whether this is a general trait of the succubi or an anthrophilia particular to the woman herself is not clear), and so she set in motion a plan to end their eons-long conflict forever, by transforming monsters into monster girls and trying to fuse the two species into one. Together with her human husband, she drove off the Chief God in battle and sent forth her daughters to rape the whole world into submission.

The Demon Lord's original plan - to cast a grand sorcery that enabled humans and monsters to interbreed - was only partially successful. Although it created the monster girls, at present their coupling with humans can only produce female offspring: that is, more monster girls, whereas the plan was to have monster girl daughters and incubus sons. Obviously, the current situation represents a slow-moving demographic train crash that'll eventually lead to the extinction of monsters and humans. In order to build up magical power to push the final stage of her plan through the Chief God's metaphysical resistance, the Demon Lord spends most of her time holed up in her castle in Royal Makai screwing her husband.