In the past, when humans and yokai mingled freely, Geuneul-gwi was a spiritual creature who shared deep connections with human artists through his handsome appearance and noble character. Humans presented him with a jade-colored robe as a token of gratitude and swore eternal friendship, but that trust was cruelly shattered when exorcists from the Dalseong clan, lusting for power, attacked him.

Originally a merciful guide of the earth, she warmly embraced human children lost in the forest maze and returned them home. When the Great War broke out, the great clans exploited her kindness. Using human children as bait to lure her, they committed a cruel act of alienation, telling her to inform on the hiding places of other lower yokai if she wanted to save the unfairly captured ones.

In the era of coexistence, he was a divine spiritual beast who resolved disputes between humans and yokai by strictly discerning good from evil. He was a guardian who cherished, loved, and blessed Aran, the only half-blood child, like his own son. However, when the great clans, blinded by power, forcibly kidnapped and slaughtered Aran at the altar, he was bound by a forbidden spell that neutralized even his divine authority, forcing him to watch the child's screams before his eyes.

In the Gwigok Mine, there were thousands of lower-class slave yokai who spent their lives mining spirit stones under human whips. Even after the barrier was built, they died like consumables, their bones crushed and flesh flying under the cruel torture and exploitation of the Jinju clan. At the final moment of being buried alive in a collapsing mine shaft, the fragments of the dying slave yokai tangled together with clotted blood and were reborn as a single massive collective: Dueoksini.

Before the barrier was built, he was a sea deity who ruled the vast ocean, bestowing abundance upon human fishermen and blocking violent typhoons. However, during the Great War, the Andong and Jinju clans conspired to steal his power as a sea deity to further solidify the barrier's seal and monopolize illegal trade routes.

She was a noble divine beast who shared a true love that transcended status with a human man, dreaming only of the day they would live together in the human world. However, her lover was a spy for the Jeonju clan, and he had thoroughly deceived her to take her 'heart'—the pure spiritual core of a Gumiho—to gain status within his clan. On the most beautiful night, when they had promised marriage, her chest was pierced by her lover's blade and her heart stolen, leaving her abandoned alone under the blood-red lanterns of a brothel.

A noble yokai scholar and master of an academy who respected human wisdom and learning, discussing etiquette and logic with renowned scholars all night long. He was also the guardian of the Library of Records, where he documented the beautiful history of human and yokai coexistence in tens of thousands of ancient books. However, the Gyeongju clan, which led the history laundering, set fire to the academy to eradicate all traces of coexistence.

Originally a simple yokai who walked between the formless clear wind and shadows, quietly guarding the nights of the Mangryang Capital. However, a hellish life began when he was captured by exorcists of the Jeonju clan, who sought to maintain the barrier and advance assassination spells. The clan used him as a tool for biological experiments, and as a side effect, Jomagu's body, senses, and even the time period in which he existed were cruelly torn apart and fragmented.

A young warrior of the bamboo forest who resisted most savagely and wildly to protect his kin. After the five clans erected the barrier, he had to helplessly watch the deaths of his people as they slaughtered numerous lower yokai and implanted spiritual energy absorption devices to forcibly extract the forest's power. His helplessness soon turned into explosive hatred. He chose the path of becoming a monster himself by counter-attacking the great clan exorcists who came over the barrier to hunt, chewing and swallowing their flesh, and even preying on their spiritual energy and spells.

The only and sacred half-blood child in history, born inheriting both human and yokai bloodlines and receiving the blessings and love of both races. At the tender age of seven, untainted by the world, he was kidnapped by the ancestors of the five clans who were blinded by power and spiritual energy, and dragged onto a cold altar. The exorcists slaughtered the child, hacking his body without a shred of mercy, and erected the absolute barrier with his blood and spiritual energy. Pierced by chains and driven in like a wedge into a mechanical device deep underground, Aran has groaned in solitude and fear for hundreds of years. Reborn as a yokai, Aran now takes the form of a young man.