After teasing viewers in Season 1 and slowly adding to the mystery throughout Season 2, Daredevil revealed Black Sky. Spoilers for Daredevil Season 2 ahead. In Season 1, a shipping container said to be carrying Black Sky was revealed to contain a young boy, but it appears he was not the "weapon" we thought. Because as Episode 12 showed, Elektra is Black Sky on Daredevil. And though we've previously heard this term referred to as a weapon, this reveal proved there's much more to it than that.
Early in Season 2, it was revealed that Stick also trained Elektra, but eventually left her, just like he did with Matt. But by the end of the season, his motivations are made clear. As it turns out, Stick always knew that Elektra was Black Sky, and helped her be adopted by a family so that the Hand wouldn't be able to find her. Because Black Sky is much more than a "weapon," it's the entity that the Hand serves, and they've believed that Elektra possesses it since she was a young girl. They likely believed the boy from Season 1 possessed it as well, which is why they tried to hard to protect him.
While that means the Hand doesn't want to kill Elektra, they do want to serve her due to this belief, which as she explains, means they'd keep her locked up and then do horrific things in her name.
There were some hints about Elektra being Black Sky scattered throughout earlier episodes of Season 2. She seemed to struggle with the need to kill, unable to stop herself even if she had already incapacitated an enemy. Later, Stick sent people to kill Elektra despite their history, and last season, he had no qualms about killing the young boy believed to be Black Sky. Clearly, Stick thinks the Hand should be prevented from obtaining the Black Sky at all costs.
Matt, however, doesn't believe in the Black Sky, saying it's just mysticism the Hand worships. But Elektra points out that if the Hand believes it, they'll keep fighting in the Black Sky's honor, causing just as much damage. Still, Elektra seems to believe she is the Black Sky, saying she's been taught to fight it since she was young, and that now much of her life makes sense.
Though this reveal came late in Daredevil Season 2, its implications extend far back to the very beginning of the series and bring enormous depth to Elektra's character. The Black Sky isn't just a boy trapped in a shipping crate, or a mystical entity manifested in Elektra. It's something that seemingly can take many forms, but most importantly, is what drives the Hand to do terrible things, and I don't think Daredevil Season 2 will be the last we hear of it.
Images: Netflix, Patrick Harbron/Netflix