SPOILER WARNING: This article contains major spoilers for "Schism," the "Arrow" Season 4 finale.
In "Schism," the "Arrow" Season 4 finale, Team Arrow won the war against Damien Darhk, but now they all need a little time to do some healing. After the battle with Darhk came to a definitive end, everyone but Oliver and Felicity went their separate ways.
The war against Darhk peaked after he arranged for thousands of missiles to strike major cities across the globe. However, with a little help from Curtis Holt and A.R.G.U.S., Felicity was able to put an end to those plans. As Felicity dealt with Darhk's missiles, Oliver went to confront the man himself as Green Arrow. The two went head-to-head, and Oliver faltered under Darhk's power until the people of Star City stepped up to help him. Oliver was then able to kill Darhk by taking one of his arrows and thrusting it through Darhk's chest, thus ending Darhk's reign of terror.
Before the Green Arrow and Darhk came to blows, however, Oliver took a gentler approach with the citizens of Star City. He was able to stop their rioting by delivering a speech of hope from atop a cab, which is what in turn inspired them to help the Green Arrow in his fight against Darhk. Oliver's speech caught the attention of the whole city, and he was offered a chance to step in as interim mayor following Ruve Adams' death. By the end of the episode, he was officially sworn in as Mayor of Star City.
As Team Arrow regrouped, each member took their leave: Quentin Lance, so that he could process Laurel's death; Thea, because she hadn't had a chance to reevaluate her life since her resurrection; and Diggle, since his brother's death left him feeling conflicted. Lance is shown to leave the city with Donna at his side, while Thea sits in contemplation in Laurel's apartment and Diggle heads off for another tour of duty, leaving Lila and baby Sara at home. This leaves Oliver and Felicity as the last two active members of Team Arrow in Star City.