John Constantine (Matt Ryan) has left his mark on Arrow.

The character from NBC’s now-canceled DC Comics series Constantineresurfaced Wednesday to help retrieve Sara Lance’s (Caity Lotz) soul after she was resurrected via the Lazarus Pit. However, the real twist came when Oliver (Stephen Amell) met the trench coat-clad, magic-wielding Constantine in the past while on the island of Lian Yu.

“That was actually a late-in-the-game brainstorm,” Arrowexecutive producer Wendy Mericle tells The Hollywood Reporter. “We wanted to explain how they knew each other in the present-day story and suddenly it made a lot of sense, given that in the flashbacks, we always intended for Baron Reiter (Jimmy Akingbola) to be pursuing an agenda, the one that [Oliver and Constantine] prevented. And we wanted to explore the idea of magic and Oliver’s experience with magic in the past, and so the flashbacks became centered around Constantine.”

After casting a spell on Oliver, which resulted in a mysterious tattoo and a promise it will come in handy in the future, Constantine’s actions will have a ripple affect all season long despite his one-off appearance.

“The outcome of that spell will come out later in the season,” Mericle says. “Constantine gives Oliver insurance against Baron Reiter. We will be true to that statement: that’s exactly what that spell is. It will come to Oliver at a crucial point when he’s extremely vulnerable and it will get him out of a really dark place.”

Below, Mericle breaks down the big episode, including what’s next for the Lance family now that Sara has her soul back, Diggle’s (David Ramsey) discovery and HIVE.

Now that Sara has her soul back, are the after effects and blood lust from the Lazarus Pit gone as well?

Even though she has her soul back, she was still brought back by the Pit. We are going to see her suffer from bloodlust. It’s going to be a major factor for her going forward. We wanted to keep it true to Thea’s [Willa Holland] journey, but Sara will experience it more intensely and in a different way than Thea.

Does that mean she’ll still try and attack Thea?

No. Now that she has her soul back, it’s going to be more along the lines of what Thea is experiencing. She’s now self-aware enough and in her own body and mind to know that she doesn’t really want to kill Thea. She can see that line.

What’s next for the Lance family now that Sara’s soul is back?

We’re going to be exploring what Lance’s [Paul Blackthorne] role in HIVE is and what Laurel’s [Katie Cassidy] reaction to that news will be when she finds out about that later down the road.

Now that Lance is playing double-agent behind Damien Dahrk’s (Neil McDonough) back, how long is he going to be able to pull this off?

We hope he’ll be able to pull it off for a while. HIVE and Damien himself with his magical powers are both so powerful that it’s one of the biggest challenges our team has ever faced. So this is the most promising way for them to try and take Damien and HIVE down, with Lance on the inside. But it’s going to be much harder than they think it will be.

Digglenow knows that his brother was involved in some shady dealings while in Afghanistan, which is why HIVE took him out. How is he going to handle this news?

In the wake of learning that information, the main emotion he’s feeling is pure devastation. He has this idea of who his brother was – a war hero, a good guy, a family man who was just caught in the wrong place at the wrong time, murdered by an evil organization. Now he’s suddenly having to rethink everything he knew about his brother. It’s like when Thea first lost Oliver: there’s a certain degree of grieving both the death of the person and the death of the person they thought they knew.

How is this going to affect his mission to take down HIVE?

It’s definitely going to galvanize him. Despite finding out his brother was involved in shady business, it doesn’t diminish his grudge against HIVE in any way. He doesn’t know the circumstances of how Andy got seduced into all these bad activities, and he’s going to be driven to find out more. He’s also going to have some heartbreaking news coming his way soon with some twists and turns.

Felicity (Emily Bett Rickards) just found out that Ray (Brandon Routh) is still alive. Viewers know what happened to him because of his upcoming role on Legends of Tomorrow. What will be the most surprising aspect about his story with Felicity on Arrow before he crosses over to Legends?

The most surprising thing for us was that we don’t feel like there is any residual tension, romantically, between the two of them. We debated a lot in the writers’ room if Felicity and Ray would try and rekindle their romance and that just didn’t feel natural. After everything they have both been through, not to mention that she’s absolutely 100 percent in love with Oliver, they are in a really good place in their friendship and there are no hard feelings between them.

Speaking of Oliver and Felicity, what can you reveal about what’s coming up for them in their relationship?

We have an episode coming up where we tell a relationship story between Oliver and Felicity that is rooted in the main Arrow story but also stands alone as the first real challenge to their relationship. It’s a different story than we usually tell.

Thea hired Alex Davis (Parker Young) to work on Oliver’s mayoral campaign, but he was initially cast as a love interest for her. What will their story look like?

For Thea, Alex represents a shot at a normal life. We want to explore Thea’s world, not just her bloodlust but also being a superhero and being a vigilante by night and a so-called normal person by day. It’s very reminiscent of the season one story we explored with Oliver. Alex is a really good guy, and the kind of guy she would have never dated normally. The fact that she’s going to fall for him speaks not only to what a great guy he is but also the fact that she’s going to have to make a choice: being a superhero or living a normal life. Or can she do both?

Arrow airs Wednesdays at 8 p.m. on The CW.