[adzii_nufc]

I believe Prometheus is merely part of a group headed by the actual Villain which I assume to be Talia Al Ghul, you can make that link by suggesting she wants to avenge her father's death. You can then back up popular theories regarding Prometheus because Talia would've had access to the Lazarus pit before its destruction.

That's merely theory though.

However its worth noting that every season makes use of Flashbacks to explain things that are key to the present day plot. I.E season 4 flashbacks eventually showed you the source of Darhk's power and where it came from. If there's no larger theory like above then its likely the origin of Prometheus and co will be explained via these flashbacks. Where the flashbacks are going this season is anyone's guess though, they have linked it to last season however by introducing a maid whom turns out to be the mother of two people Oliver killed on the Island.