Dark Shadow

Dark Shadow is a Quirk used by Fumikage Tokoyami.

Description
This Quirk allows Fumikage to host a shadow-like monster within his body. Fumikage can use the shadow-like monster for a number of purposes, such as attack, defense and support. This shadow-like monster has shown to be sentient. The shadow-like monster has an energy limit and when it runs out, the shadow like monster will retract back into Fumikage.

The personality, power and control of the shadow-like monster depends on darkness and light:

Under the power of light, Dark Shadow is weaker but despite this, it still has extraordinary defensive skills as it was able to completely block Katsuki's Explosion without suffering any damage and was able to block Denki's electricity (despite having weaknesses to them due to the light they produce). Dark Shadow's personality under light is docile, allowing Fumikage to control it with ease.

Under the power of darkness, Dark Shadow becomes more larger and ferocious and as a result far more powerful. One of Dark Shadow's claws was able to rip through a tree with ease when trying to attack Izuku. Dark Shadow's personality completely changes when surrounded by darkness, becoming berserk and attacks indiscriminately. It appears keeping Dark Shadow under control during the night where darkness is most prominent is a great struggle for Fumikage as it requires all his focus. Once Fumikage loses control, Dark Shadow starts enveloping Fumikage's body with its darkness and attempts to take control of Fumikage.