Board Thread:Television/@comment-3048593-20180113175532/@comment-1894786-20190314014701

KalKent wrote: Also, I might be wrong on it, but I got the idea that the Black Sky was supposed to be a weapon of Hand. Main issue they had was keeping Elektra in control being that. Just an interpretation.

Judging by context clues, it seemed like the Black Sky was supposed to be what the Iron Fist was to the Chaste; their leader, their most powerful warrior, and able to manipulate chi in some form.

And apparently there was also a prophecy about the Black Sky that was convincing enough for Alexandra to risk it all on Elektra. But sadly we never got any of that background.