system
Given the following post, respond as if you're commenting on Reddit:
human
[MCU Daredevil] So what is a Black Sky?

It's never really said what the significance of the child (or Elektra) is, but Stick and the Hand definitely act like it's a big deal.
gpt
The're a person, but something more than a person.  A spirit in human form.  The reincarnation of a demon.

The black sky is phenomenally good at killing, and can become undefeatable with the proper training.  They're also naturally inclined to kill and injure others, they *enjoy* it, and will do so even when it may be inappropriate.  A black sky is usually identified as a child when a child prodigy at martial arts "accidentally" kills (or nearly kills) a fellow student who they were sparring with.

A Black Sky is a dangerous creature that will cause great harm to the human world on its own.  It can also be used in a variety of rituals that cause *even worse things* to occur.  It is related, in some way, to the ability of members of the Hand to resurrect themselves and others.