|Spoiler Alert: This article/section contains details about future plotlines of LOTM: Sword of Kings described. Do not proceed unless you want to be spoiled. |
Black Demons are a race of creatures which are born from Mortal souls who, for various reasons, do not cross over to Afterlife after their death and stay in the Living World for too long. They are corrupt spirits with supernatural powers which devour the souls of both living and deceased setient beings. Black Demons settle in Qliphoth, but can cross over to the Living World and Afterlife. Black Demons are the opposite of Spirits and a near-biological race to Inverse Spirits.
Through the story of LOTM: Sword of Kings, the Black Demons are a predominant antagonistic race to Magic Side of the storyline and are connected to almost all incidents of the story. Despite they're souls who were stuck in the Living World, the Black Demons came to exist when Idea of Evil sent its black essense to Hell, where some demons were infected by it with only one being made of this black essence, Ara Astaroth. When Ara started her campaign for power and revenge by founding the Revelation of Qliphoth, several demons who followed Ara became Black Demons after drinking her blood, infecting them with Idea of Evil's evil blood and giving them vast powers beyond a High-Class Level Demon. In other words, souls of mortal beings who died and could not go to Afterlife, were infected with the Blackness and became Black Demons against their will while several demons accepted to become such thing.
OverviewThere are 2 ways to become a Black Demon; BD are former ghosts who lose their hearts to despair or regret, or they remain in the Living World for too long. Any spirit who is not guided to Afterlife by a Spirit Guide may eventually turn into a Black Demon if it's exposed to the Blackness from Ara Astaroth's evil aura that has been corrupting the Omniverse for centuries. Other method to become a Black Demon is if the demon himself or herself accept the Blackness, abandoning their former identity to become stronger.
The majority of ghosts peacefully move on to the Afterlife after their death. However, some stay in the living world to fulfill certain goals, such as looking after a loved one, protecting a particular location, or pursuing a grudge from beyond the grave. However, with only limited abilities to interact with the living, and by definition tied to their goals, many ghosts find they are unable to cope when their loved ones move on or old enemies forget them. At this point, some will become dangerously obsessed with fulfilling those goals, even if the means to fulfill them renders the soul empty: for example, killing anyone who comes near a loved one in order to keep them from hurting that person. In doing so, the ghost warps into a Black Demon (even without being infected by the Blackness) and, ironically, often makes the focus of their obsession into their first victim.
The process by which a soul becomes a Black Demons usually takes months to years to complete, reflected by the length of the soul's Chain of Fate, which usually resides in the center of their chest, and connects to their bodies, if present. The Chain of Fate slowly corrodes over time, coinciding with the degradation of the soul's ties to the living world. The process can be accelerated under certain conditions, such as being attacked by a Black Demon, giving into extreme despair, or using certain spiritual powers. When the chain completely decays, they become a Black Demon when a hole opens up on their chest where the chain was attached, signifying they have lost their heart.
Once a soul or demon becomes a Black Demon, it is driven by an eternal and insatiable hunger to devour other souls, living or dead, to fill the void caused by its descent. While their former obsession often becomes their first target, most Black Demons will eventually become mindless creatures concerned only with finding the most potent souls to devour. Stronger and more evil Black Demons (like deceased serial killers, murders, rapists etc...) are often able to retain some of their intelligence in Black Demon form, making them more dangerous than the average Black Demons like the soldiers from Black Army. While most Black Demons are evil, or at the very least mindless, at least a few are not, as is the case with Tomas and Black Hanekawa's companions. They are at least partly capable of camaraderie and loyalty, as seen with Krulcifer and her companions while they were still Black Demons.
A Demi-Black Demon is a Hybrid Demon-Ghost, an earthbound spirit who is evolving into a Black Demon. It usually takes a while for the earthbound spirit to fully transform into a Black Demon, but this process can be sped up by forcing the hole in their chest to open. The Demi-Demons are held down by chains, usually to a place they consider to be their territory. They are usually only seen when a mortal steps on their territory and cannot be easily sensed by Angels and even humans; which is why humanity has called them as ghosts or people who died with remorse and often haunts the place where they died.