Without question the biggest question of this season has been the identity and motives of Prometheus. While we now know the former we don’t know the answer to the latter but after re-watching key episodes I think I have an idea of what Prometheus’ plan is, and how deep it goes and how he knows everything he does.
I think his name “Adrian Chase” is an just an alias and that his parents really are Justin Clayborne and Amanda Westfield. Despite Clayborne’s ruthlessness, I think he did genuinely loved Adrian like any father loves their son and Adrian overlooked his flaws. Or perhaps Adrian wasn’t aware of the monster his father really was. Then when The Hood killed Clayborne in 2012 Adrian became as vengeful as anyone who losses their family to a “murderous bastard”. After all let’s face it while Oliver was doing some good he left a lot of collateral damage in his wake, and the people he killed knew people who would see vengeance which only spawned more evil. Also note the names of his parents Amanda and Clayborne, as in A and C, which makes “Adrian Chase”.
After Clayborne’s death Adrian sought vengeance and learned Oliver’s identity and trained himself to fight everyway Oliver knows, and achieved this by seeking out Talia al Ghul. After all she basically created Green Arrow so fitting that she creates Prometheus as I am convinced that whatever Adrian’s motives are, he and Talia are in league against Oliver. Most likley Talia is either vengeful for Oliver killing her father or she sees Oliver, who she inspired to become Green Arrow, as a failure and Prometheus is her literal example of how Oliver's failures led to Star City almost being destroyed countless times now.
Talia is also probably where Adrian learned about time travel and the Multiverse as Talia has probably been keeping tabs on Barry, and no doubt learned of his future rivalry with Reverse-Flash and inter-demensional war with Zoom last year. Talia also met Sara as a child from 1958-1960 and probably kept tabs on the Waverider's sightings throughout history from the point on. Eventually she would have discovered Sara’s time-of-origin probably while studying Oliver. With Adrian armed with this knowledge he would have learned the identities of every Team Arrow member and studied them to fine detail that he knew exactly how each of them thought then from 2012-2016 continued training himself and planning everything to perfection. As a result he'd know every move they’d make and since he was spying on the team the whole time he would simply adjust the circumstances of his plan if the situation required it, such as the team encountering meta-humans and magic.
However I think Adrian has another equally driven motivation which took place long before his father’s death which he didn’t even realize until many years later after. This would have only further added to his anger and even adjusted his entire 5 years plan to accommodate for it. Adrian mentioned in 5x03 to Oliver that they first met 12 years ago, which at the time would me sometime in 2004, when he hocked up with his girlfriend who left Adrian for Oliver. I think this girl was in fact Laurel Lance as she and Oliver had been dating for some time by 2005. I think afterward Laurel and Adrian probably would have still known each other as they were both attorneys and probably both went to law school together after the breakup, and Laurel probably insisted on just remaining friends. While Adrian would have respected Laurel’s wishes he probably still loved her anyway and then in 2016 when she was killed, Adrian probably blamed Oliver because if he wasn’t Green Arrow, then Laurel may not have become Black Canary. Adrian also did say when telling Oliver about his ex-girlfriend "It's ok I don't hold grudges" in a very Oliver-way of saying it, and as we've no doubt seen he does indeed hold a grudge.
I think through intimidation and manipulation Prometheus is plotting Green Arrow’s ultimate downfall and he can’t even see it yet. Prometheus staged Billy as himself knowing Oliver would kill him which caused him much grief but after Adrian insisted on covering up the incident to prevent panic, and then he leaked it to the public which forced Oliver to label Green Arrow as a criminal in order to keep his seat in office which tainted his image. This shows that Adrian obviously knows Oliver quite well and knows exactly what he’ll do to protect those he loves and is manipulating him into becoming the cause of his own downfall, and to ruin everything he built for himself and prove once and for all that he is the villain of his story. There are also two major factors that have driven the second half of the season but if one looks closer enough, they were both caused by Prometheus' manipulations and I think there is more to it that we haven't yet seen.
Prometheus tricked Diggle into getting arrested again but then Adrian represented him and managed to exonerate him after Felicity obtained the Pandora file to leak the information on General Walker. I think Prometheus staged John’s arrest precisely so Felicity could obtain Pandora, knowing the lengths she’d go to exonerate him, as Prometheus plans to use it himself later. However Prometheus couldn't obtain it himself but knew Felicity could and with the reputation she has as a hacktavist, would. Remember Pandora has information on virtually anyone who has something to hide in the world and Star City is filled with corrupt buisnessmen. I think Prometheus is going to start some kind of political/economic uprising by releasing Star City’s dirtiest secrets to the public to cause all out anarchy, yea Anarky himself would love that lol. What's worse is there is nothing Team Arrow could do because it isn't just another terrorist attack which they've prevented before. This time the chaos is caused by the people within the city itself and Prometheus will watch as Star City tears itself apart, becoming the source of it's own undoing. Therefore Prometheus proves that Green Arrow is poison and his efforts to save Star City have only led to it's death, and everything he spent the last 10 years fighting for is lost.
Also Prometheus freed Black Siren to confront Green Arrow and after she was incarcerated yet again, Oliver decided to keep his promise to Earth-1 Laurel and find a Black Canary successor which led to him meeting Dinah Drake. I think Prometheus used Earth-2 Laurel precisely so Oliver would keep his promise, knowing how much Oliver loved Earth-1 Laurel and that encountering an evil version of the woman he loved would be sufficient motivation to keep said promise. I don't think Adrian planned on Oliver recruiting someone with Earth-2 Laurel's powers, just someone to pick up the mantle. Like I said above I think aspects of Prometheus' plan have changed over time with the new elements that have come into play over the years. Why would Adrian wants this? I think Prometheus is planning on killing Dinah to prove to Oliver that everyone he comes into contact with dies, and Oliver only sought Dinah out to honor Laurel’s memory but if Laurel hadn't been Black Canary there wouldn't be a memory to honor as she wouldn't have died, or at least that's how I think Adrian sees it.
Furthermore while he have seen that Adrian Chase and Vigilante are separate characters there was a moment in 5x15 when Vigilante looked at Dinah and even had to zoom in on her, almost like he was confirming her identity which implies he knows her. Dinah had been traveling the country from 2013-2017 and only just moved to Star City so Vigilante shouldn't even be aware of her existence. I think that particular version of Vigilante was actually Prometheus moonlighting as him while there is an actual Vigilante, who is the one we see fighting Prometheus and later Spartan, Wild Dog and Mr. Terrific which is further proof of my speculation about Prometheus' plan for Dinah. Also because "Vigilante" attacked the limo the hearing was pushed back which gave Oliver enough time to reconsider who he labelled responsible for Billy's death, because if this hadn't happened chances are the councilmen would have just fired him. Again when Vigilante attacked Oliver in the limo Adrian wasn't there then he was and when he took Vigilante's piece of tech from Dinah, he acted nervous like he's hoping his DNA doesn't get found on it. After all what better way for a villain to target a hero then by using another more unhinged version of the hero he's targeting as his scapegoat?
This season is about legacy in two forms: the living and the dead. The living is Oliver, his drive to save the city only to be haunted by all the bad he’s done to the extent that he’s stopped seeing all the good he’s done the latter of which certianly far outweighs the former. The dead is Laurel, and how her death shaped many of Oliver’s actions this season in his drive to be the hero Star City needs him to be. I think it would be logical if Adrian’s actions were the result of both Oliver and Laurel's legacies making him the ultimately legacy villain.