Arrow star Stephen Amell and executive producer Marc Guggenheim preview what fans can expect from the second half of the season.

Mirakuru

In the mid-season finale, “Three Ghosts,” both Slade Wilson and Roy Harper survived injections of mirakuru, the effects of which Arrow executive producer Marc Guggenheim describes as “sort of ‘roid rage.”

The writers put a lot of thought into grounding the effects of mirakuru before introducing it, considering “the closest real-world analogue,” Guggenheim says. “We let that be our compass — that’s what helps us keep the show grounded and not too science fiction-y.”

Like steroids, mirakuru “gives incredible strength, speed and endurance, but it also comes with cognitive impairment,” Guggenheim explains. It “draws out” anger, thus making Slade the vengeful figure we saw in the mid-season finale as well as putting Roy through the wringer.

“Things will get worse for Roy before they get better,” Guggenheim says. Episode 12, titled “Tremors,” in particular will explore Roy’s difficulties after being injected with mirakuru.

Rogues gallery

As for when Slade and Oliver will cross paths in the present day, Guggenheim teases, “We always do things sooner than anyone expects, but that said, as Slade alluded to at the end of episode 9, it’s been five years since they saw each other on the island.”

The EP describes Slade’s plot to create an army of mirakuru-enhanced soldiers via Sebastian Blood’s experiments as “a very long game” since “just killing Oliver is too simple and too merciful.”

As if Slade’s vendetta isn’t enough for the Arrow to deal with, we can also look forward to the return of the Bronze Tiger (Michael Jai White) and the appearances of the Clock King (Robert Knepper) and Nyssa al Ghul (Katrina Law), daughter of Ra’s.

“We don’t say a character’s name unless that character is going to factor in. We don’t hint at something unless we’re going to pay it off,” Amell teases, likely in relation to Nyssa, as Ra’s and his daughter have been repeatedly mentioned in relation to Malcom, Sara Lance, and the League of Assassins. Nyssa will appear in episode 13, “Heir to the Demon,” an episode Amell says belongs to the Lance family.

Meanwhile, the Clock King will appear in episode 14, titled “Time of Death,” an episode that Amell says hints at the season’s endgame. “[A]t the end of episode 14, we end in a spot where we get our first glimpse on where we are going to end after 23 episodes. That’s what I’m most excited about because I want people to see it.”

Keeping up with…

Another plot point that has been mentioned is Thea’s parentage; we learned at the end of episode 7 that Malcolm is actually Thea’s father, the result of a short affair between him and Moira Queen.

“I think that we would have to expect that sooner or later Thea will discover the truth, that sooner or later Oliver will discover the truth, because we’re not going to have John Barrowman lurking around our world and go an entire season without the two of them having a confrontation again,” Amell says.

Fans can also expect to periodically hear about Barry Allen. In the mid-season premiere, for instance, we learn that Felicity has gone to Central City to spend time with Barry, who has been comatose since his accident after the S.T.A.R. Labs particle accelerator malfunctioned.

“We honor the relationship that Felicity formed with Barry, and we honor the emotional reaction to his accident,” Guggenheim says. “It’s not all swept under the rug.”

Vigilante to hero

Meanwhile, Oliver will struggle with making the transition from vigilante to hero. “His vow [not to kill] gets challenged by all the things he’s facing,” Guggenheim previews. “It’s one thing for him to say he’s a hero, but now he’s called upon to really be a hero.”

However, “[i]t’s not just the no-killing code.” Oliver has “to find a new gear and dig deeper and overcome tougher obstacles. He’s got to bring people closer together and be more of a leader, even as that gets much harder. And on the other side of the board, Slade is manipulating events against him.”

“The struggle for Oliver is,” Guggenheim adds, “how does he adhere to the objective he set for himself of being a hero when things in the city start to get worse and worse?”

This struggle is essential because, as Amell teases, “What we are building towards in the second season is very much one giant group on one side and one giant group on the other side…coming head‑to‑head. So we are populating our world in the second season for a very specific reason, and I can’t wait to see the results.”

Arrow season 2 returns on Wednesday, January 15 at 8:00 p.m. ET on The CW.

What are you most looking forward to in the second half of ‘Arrow’ season 2?