'Arrow': SPOILER Returns, But With a Twist in "Fundamentals"

Tonight's episode of Arrow put its title character through the ringer -- with the help of a familiar face.

Spoilers for tonight's episode of Arrow, "Fundamentals", below!

The episode saw Oliver Queen (Stephen Amell) pushing people in his life away, as the fate of Team Arrow and of himself as mayor hung in the balance. After a fight with Felicity Smoak (Emily Bett Rickards), Oliver returned to the Arrow bunker where he was met by Adrian Chase (Josh Segarra), who had been presumed dead after carrying out his master plan in the Season Five finale.

Oliver and Chase fought each other, culminating in Oliver snapping Chase's neck. But soon after, Chase returned back to life, making it clear to Oliver that he was under some sort of hallucination.

As the episode went on, Oliver revealed that he had been poisoned with Vertigo by a corrupt member of the City Council, something that he was reminded by with Chase's frequent presence. Chase then essentially took Oliver on a tour of some of the worst moments in his life -- namely, lying to Earth-1 Laurel Lance (Katie Cassidy) and getting on the Queen's Gambit before Season One, and then letting Laurel die at the hands of Damien Darhk years later. Throughout it all, Chase was taunting Oliver, arguing that his personal decisions have been a bigger downfall to him than any enemy.

Oliver tried to bounce back from the Vertigo, attending a City Council meeting about his pending impeachment. But throughout it, Oliver was continued to be haunted by Chase, leading to him butchering the meeting and furthering suspicion.

Chase then convinced Oliver to single-handedly take on Ricardo Diaz (Kirk Acevedo) and his men, and kept Oliver convinced even as Felicity tried to intervene. Ultimately, Oliver ended up returning back to his senses, but was still affected by what Chase said.

While those involved with Arrow had been teasing some sort of character return in this episode for quite a while, the reveal of having it be Chase was certainly somewhat unexpected. And in a way, that fits the villain pretty perfectly, considering the unpredictable tenure he had during Arrow's fifth season.

"We were looking for something different to do in Season 5, a way to change it up and make it different," executive producer Wendy Mericle told ComicBook.com last year. "The comic book characters are great, and they usually do end up in sort of a physical duel. We really wanted this to be different and have Prometheus be somebody who is manipulating and torturing Oliver, more psychologically than anything else."

What did you think of this surprising return in tonight's Arrow? Let us know in the comments below.

Arrow airs Thursdays at 9/8c on The CW.