Dark Shadow

Dark Shadow is a Quirk used by Fumikage Tokoyami.

Description
Dark Shadow grants Fumikage a shadowy monster-like being within his body that he can materialize and de-materialize at any moment.

Dark Shadow is always connected to Fumikage's body, even when it moves itself far away from him. However, Fumikage does not appear to share the same physical sensations as Dark Shadow, such as pain and weakness, and vice-versa. Dark Shadow is apparently made of "darkness energy", despite being a solid entity that can interact with the material world. It's also sentient, capable of speech and loyally protects it's host regardless of the state it finds itself in. It also seems to be able to communicate telepathically with it's host, if it's too far away to speak.

Dark Shadow has an energy limit, retracting into Fumikage's body when said limit runs out. Fumikage has implied that there's a way to recharge this energy, but it's unknown how he does it.

Usage
Fumikage primarily fights from a distance, ordering Dark Shadow to fight on his behalf. When he needs to defend himself, Fumikage lets Dark Shadow handle the opposing impacts for him. Dark Shadow also helps Fumikage with mobility, supporting him if necessary. Dark Shadow mostly attacks by stretching or growing both of its arms, using them to grab or slam the adversary while Fumikage stays out of danger. This grants Fumikage a huge advantage in one-on-one battles, to the point of being viewed as almost invincible.

Dark Shadow's personality and offensive power depend on the surrounding brightness levels. Under strong light, Dark Shadow is small and weak in comparison to when its engrossed by darkness. Even so, Dark Shadow maintains extraordinary defensive skills, as it can still block light-creating Quirks such as Explosion or Electrification with some efficiency. Dark Shadow is docile when exposed to light, making it easy for Fumikage to control.

Under little to no light, Dark Shadow becomes a large and ferocious beast with incredible offensive ability. One of Dark Shadow's claw attacks can rip through dozens of trees with ease in this state. Moonfish, a veteran villain, ended up completely overwhelmed and defeated by Dark Shadow's powered up form, having his own defenses obliterated in a single strike. Dark Shadow's personality under the influence of darkness is the opposite of when it's exposed to light, becoming far more unruly and vicious while attacking anything that moves or makes sound indiscriminately.

According to Mezo Shoji, Fumikage's negative emotions (such as regret and indignation) can intensify this version of Dark Shadow, giving it enough power to defy Fumikage's commands and gradually take over his body with its expanding darkness. Once this happens, Dark Shadow is able to force Fumikage to move around against his will, leaving Fumikage with no control over his body.

Named Super Moves

 * Black Ankh: Fumikage's special move (previously known as Tenebrous Abyss Body (深淵闇躯), he dons and equips Dark Shadow onto himself, wearing it like a suit of armor or an exoskeleton. According to Fumikage, equipping Dark Shadow onto himself mitigates his physical weaknesses.
 * Piercing Claw of the Dusk (宵闇よりし穿つ爪): Fumikage swiftly extends Dark Shadow's claw from his arm to attack from a distance.
 * Gloom of the Black Arm (黒き腕の暗々裏): Fumikage enlarges both of dark shadows arms and crushes his targets.
 * Black Fallen Angel (黒の堕天使 Kuro no Datenshi): It is a technique that Fumikage devised under the tutelage of the Pro Hero Hawks. Fumikage wraps himself up in Dark Shadow's arms and allows himself to be carried by it, while Dark Shadow flies by flapping its arms as wings.

Trivia

 * Like several other Quirks, Dark Shadow has its own signature sound effect: "CREEP".