** I've been meaning to write a one shot using this quirk but haven't been able to develop a good story yet. Thus, I leave it to you guys to use as you please. Though if you do write a story please tell me about it cuz I would love to read it.**
Ruler of the Negative Void:
The user is able to access a realm parallel to planet Earth known as the Negative Void. It originated from the mix of chaotic energy and bad karma generated by humans. Feelings such as hate, resentment, agony, wrath, suffering, frustration, and jealousy; the senseless massive loss of life, and destruction that comes from human greed and desire for power (countless battles and wars over the entirety of human history), all of this is what makes up the Negative Void. An infinite amount of malicious entities have been born out of Void's dark energy and the user is able to both access this world, harness some of its power, and exert control over most of the denizens. Due to the parallel nature of the Void, accessing it can only be done through shadows or darkness itself meaning that the user's power works best in the dark.
They can bend some of the Void's energy to their will and use it on themselves. However, to do this they must offer a little bit of their vitality as an offering to call forth shadow entities that can take any shape from appearing as simple raggedy looking shadows to monstrous creatures. Alternatively, he can offer up some of his own blood, and flesh including that of his opponents to summon a stronger but more dangerous monster. The most powerful summon can be brought forth if he offers a soul to it and it is the most human-like of all of the Void creatures called a Fracture. The stronger the entities summoned, the more intelligent they are, and the harder it is to control them.
The residents of the Void are as follows from weakest to strongest:
Shards: They are called this because they are small bits of negative energy that have managed to become a moving shadowy physical manifestation.
**Photo not mine, credit to its creator**
They are most numerous and weakest in the Negative Void since they lack a sense of self/ego, are pretty much mindless, and as such they readily follow commands without question even causing their own destruction if ordered to.
Fragments: entities that have medium power levels as they have some loosely sense of self and primitive intelligence. They are much bigger 'pieces' of negative energy that has manifested in the Void. However, they are aware of their existence (aren't midnless like Shards) and but have no real ego/personality.
**Photo not mine, credit to it's creator**
They do not have names, have basic intelligence and, will only recognize/follow the commands of the strong. Consuming weaker Shards or other Fracgments is how they get stronger and can eventually evolve to become a Fracture.
Fractures: the strongest and most dangerous creatures of the Negative Void. These are the biggest physical manifestation of negative energy that has managed to acquire a complete sense of self, a strong personality to the point of creating a name for themselves and have medium to very high intelligence. They are almost impossible to control and will only approach if they are interested though most wish to kill the user and use their body to escape the Void. The appearances of Fractures varies widely based on their personalities and how strong they are. However, it has been noted that the more human-like they are, the more power they possess since they have compacted and condensed it into their bodies.
Moreover, due to the aggressive and proud nature of Fractures. The user will only ever be able to subdue and control 1 single Fracture at any given moment. If they attempt to control more, they will lose control of both Fractures as the entities will fight to consume one another in order to become stronger. Also, Fractures that manage to do this will ALWAYS try to kill the user next as they will be bursting with tremendous power and blinded by uncontrollable bloodlust.
**Photos not mine credit to their creators**
Regardless of their power and intelligence level, all of the Void inhabitants can communicate with the user through telepathy eliminating the necessity of giving verbal orders. Besides telepathy as a way to communicate with the shadows, the user can teleport within the darkness or the surrounding shadows. This makes traveling the entire world both possible and easy as it doesn't require any energy (they use the shadows as an Uber basically).
Additionally, the shadows that are called forth can act as extra eyes, ears, and as a way of touching targets akin to a two way mirror. Allowing the user to spy on other people remotely (your own shadow won't be able to keep your secrets). Moreover, the user can also hide a summoned Void monster in the shadows either to serve as a bodyguard or as a way to track targets. In addition, the user can utilize a denizen of the Void (usually Fragments) to overpower a target's mind and make them a living puppet. When the user takes control of someone that person's stamina, quirk power, and proficiency become twice as strong. Furthermore, Ruler of the Negative Void feeds on all the negative emotions, fears and insecurities of targets, making the both user and the summons stronger.
Once the denizens of the Void have been summoned, they have to be physically destroyed in order to be eliminated because they have already becomed stable tangible entities. However, destroying them cannot be done using human weapons and they don't really 'die' since they are merely banished back into the Void. This is because a summoned creature can already sustain and strengthen themselves without the need of their master's vitality. They do this by consuming human emotions (especially negative ones) and/or killing humans to absorb their life force = souls.
Nonetheless, they normally do not kill recklessly unless ordered, if the user's life is on the line, or if it's a Fracture that has becomed uncontrollable. If the latter one occurs then both the user and those around become targets as the Fracture will try to devour them to continuously get stronger.
Now, another dangerous but undeniably useful ability of Ruler of the Negative Void is that the user can actually have the summoned monsters consume people. When this occurs, the user can permanently acquire more stamina, physical strength, agility, and life force for themselves (can become biologically immortal by continuously eating people) . Also, by devouring a target, the drawback effects of quirk usage are reset and the user can use their ability for much longer. For this reason, this ability is rightfully called: Dark Harvest. When quirk is active, the sclera of the eyes turns black while the pupils burn a bright neon purple.
Drawbacks : Photo sensitivity, auditory hallucinations (at least that's what it looks to others since only the user can hear/talk to the creatures of the Void), temporarily becoming more violent/aggressive due to the influence and nature of the Void, mental confusion, hypersomnia, exhaustion, and loss of consciousness if overuse is severe enough.