Arrow finally name-dropped the Ninth Circle - a sinister group from the Green Arrow comics, who was theorized to be the organization run by the terrorist financier called Dante; however, the season 7 episode "Inheritance" ended with a twist by revealing that the true leader of the Ninth Circle (and season 7's real villain) isn't Dante but the new Green Arrow, Emiko Queen.
Although their name wasn't spoken until "Inheritance", the Ninth Circle has been involved in nearly every aspect of the present-day storyline of Arrow season 7. It was the Ninth Circle who were responsible for stonewalling an ARGUS investigation into corruption in the Pentagon and the Department of Defense. The Ninth Circle was also revealed as the organization responsible for financing crime-boss Ricardo Diaz's efforts to take over Star City in season 6 and his hiring the assassins known as the Longbow Hunters.
The Ninth Circle was revealed after Oliver saved a scientist's life, who had helped the group steal military-grade drones from Palmer Tech. This led Oliver to discover that Emiko worked for the Ninth Circle, though she claimed that she had been recruited as a young girl and trained as a warrior so that she could survive after being abandoned by their father. While Emiko was telling the truth about how she came to join the Ninth Circle, she didn't tell Oliver that she wasn't being blackmailed to continue serving the organization. She also didn't tell him that she was the current leader of the Ninth Circle and that Dante, the man who recruited her and taught her how to fight, now answers to her.
The final present-day scene in "Inheritance" also seems to confirm another theory regarding the Ninth Circle and them being responsible for the woes of Star City in Arrow's season 7 flash-forward storyline. In this scene, Emiko shrugs off Dante's concerns that the rest of the Ninth Circle's leadership is starting to lose confidence in her and notes that she made a major discovery during her time pretending to work alongside Team Arrow. She goes on to describe the Archer Program - a security system designed by Felicity Smoak that evolved into a surveillance system capable of tracking a person's DNA signature across a city - and the sort of power that technology could give the Ninth Circle.
In the flash-forward storyline of Star City 2040, it was revealed that the Glades - formerly the worst neighborhood in Star City, now a high-tech gated community for the rich and powerful - is continually monitored by the Archer Program. Galaxy One, the company that runs the Archer Program on behalf of the Glades' local government, was also revealed to be a front for a terrorist group called the Eden Corps. With the Ninth Circle already financing several terrorist groups in the modern day Arrowverse, it doesn't seem like a huge leap to suggest they are the power behind the future terrorist group that controls the Archer Program. It remains to be seen, however, if Emiko Queen can successfully take control of it in the modern day, as Arrow season 7 continues.