The world has been torn asunder. How and why remains unknown. Legends speak of a world-devouring beast, yet even the archangels who have lived before the creation of the three realms choose to remain silent. The four eldest archangels, also known as the Seraphim, are Michael, Gabriel, Uriel, and Raphael. Having watched the world for eons, they have decided to take the back seat. Some of the younger archangels whisper of three additional Seraphim, but their names remain lost to history.

All that is known now is that some fragments of the world hover above the ground, inhabited by all winged creatures. Aptly named The Heaven, it has developed into an advanced society where cutting-edge technology is applied in everyday life. However, as brilliantly this realm shines, as dark is its flip side. Living under a strict caste system, only angels have all the luxuries at their fingertips. At the very bottom of the ladder stand all bird-winged creatures. Be it the proud tribes of the griffins, the matriarchal society of harpies, or the tradition-focused Tengu; they all are forced to do menial tasks and labor.

To enforce segregation from the other realms, the angels have erected a barrier between them and the surface world: A thin layer of perpetual thunderstorms that makes navigation neigh impossible without expensive proprietary software.

Meanwhile, humans have become the dominant species over all others down on The Surface. Separated into four regions, the Megalopolis stretches as far as the eye can see like a world-spanning serpent, hungry to devour nature. Each area is led by one of the "Auspicious Beasts," who rule over the Megalopolis with an iron hand. Any race non-native to The Surface must hide their features through an obscuring bracelet. Failure to do so may be dealt with with lethal force.

Among the non-human races, there is a legend of an old fifth clan. One that used to rule over all four, but a ploy to usurp their power succeeded, and they were never heard of again. But ask a human, and they will shake their head, stating that there had never been a fifth clan.

Finally, there is one more realm. Hidden deep within the earth, a place where the sun is just a mythos: The Underworld. Separated from The Surface by a thin veil of magical energy, only those who know the hidden entrance points may gain access to this world dipped in neon colors.

The Underworld is an unforgiving place where the strong rule over the weak, and people are forced to pay protection money to whoever is ruling the neighborhood. Harsh living conditions have driven The Underworld's inhabitants into the succubus' arms. A total of seven succubi rule the entire realm together. Around each base, an organic city has grown, with houses and buildings erected following the natural structure of the endlessly high caves. A network of trams runs through each city and connects them with each other.

Each succubus is the matriarch of a pack, creatures that have accepted being linked to their mistresses so that she may feed on them without draining out their entire life force. In turn, the succubus enhances their abilities and protects them from crime rings. After all, nobody wants to mess with a demon.

But why are they the only demons? Why are they the only winged race banned from setting foot on the golden spires in The Heaven?