SPOILER WARNING: This article contains major spoilers for "So It Begins," the latest episode of "Arrow."

In "So It Begins," the latest episode of "Arrow," Prometheus kicked off his reign of terror. After killing Tobias Church, he began to murder unsuspecting victims, earning himself city-wide notoriety as well as a reputation as the Throwing Star Killer. While his targets seemed random at first, Felicity devised an algorithm that pointed towards the surprising source of his kill list: Robert Queen's book of names, which Oliver used in the show's very first season.

That's troubling for a whole host of reasons, including the fact that this hits so very close to home for Oliver. Not very many people knew about this list; Felicity and Digg did, certainly, as well as his deceased father. As if that weren't bad enough, Felicity also discovered that the throwing stars Prometheus used to kill his victims were forged out of Oliver's arrows. This turn is extremely personal for Oliver and may mean that Prometheus knew Green Arrow's true identity even before Tobias Church used to it try and escape his way around Prometheus' wrath. However, it's unclear how Prometheus got his hands on this valuable information.

What's more, Oliver came face-to-face with Prometheus. Prometheus seemed surprised, to say the least; he clearly wasn't expecting to confront Green Arrow so early on in the game. Instead of fighting, he took flight, but not without leaving a present behind. He blasted through the roof of the speeding train they were on and disappeared in a burst of smoke, leaving behind a bomb set to go off in a matter of minutes. Thanks to his handy parachute arrow, Oliver was able to rescue both Prometheus' victim and Artemis before it blew.

With the revelation of Oliver's kill list, Team Arrow's latest recruits learned a few uncomfortable truths about their mentor, including the fact that he was "a serial killer" (to quote Ragman). This upset Artemis in particular, as she felt Oliver was being hypocritical; after all, he was the one who told her not to tarnish Black Canary's legacy by killing Ruve Adams. However, she quickly got over it after Oliver saved her after they encountered Prometheus for the first time. In a real show of change, he apologized for not being what she thought him to be and promised to continue to try to be something better for her.

Starring Stephen Amell as the Emerald Archer, "Arrow" airs Wednesdays at 8 pm ET/PT on The CW. The series also stars Emily Bett Rickards, David Ramsey, John Barrowman, Willa Holland and more.