SPOILER ALERT: Do not read if you have not yet watched “Crisis on Infinite Earths: Part Two,” the “Batwoman” episode of the 2019 “Arrowverse” crossover.

The second hour of the CW’s “Crisis on Infinite Earths” crossover killed off another iconic hero — but brought one back.

After Oliver (Stephen Amell) sacrificed himself in event’s first episode, Barry (Grant Gustin) and Oliver’s daughter, Mia (Katherine McNamara), refused to accept his death was permanent.

In an attempt to reverse course, they recruited a very reluctant Sara (Caity Lotz) to find a Lazarus Pit in the multiverse to revive the fallen hero. Thanks to an assist from Constantine (Matt Ryan), they were able to bring back Oliver — but without his soul.

With the Pit revivals traditionally leading to extreme aggression, “it’s not just an easy transformation that you go in the Pit and then you’re back,” “Arrow” executive producer Beth Schwartz points out.

Keenly aware of this is Sara, who was also revived by the Pit and struggled in the aftermath. “It really gives her some real skin in this in this game,” “Legends of Tomorrow” executive producer Keto Shimizu says. “It’s another reminder for us of how far she’s come. … This whole event is really important for her arc.”

Executive producer Marc Guggenheim adds that Sara went into the “whole Lazarus Pit idea with Mia and Barry with a lot of reservations…that are very, very well earned.” So the fact that Oliver has returned without his soul is “just another confirmation that she should have maybe trusted her original instincts. Things are not working out quite the way Barry and Mia had hoped.”

After reviving a number of dead characters with the Pit, the “Arrowverse” had previously taken them out of play, making death a more permanent fixture on the franchise. However, with two episodes still left to go in the series in which Oliver is the titular hero, killing him off in the crossover couldn’t follow that pattern. Instead, the producers feel that even with the side effects, making death reversible (again) has the potential to change the stakes for an event this big — although they are reluctant to say exactly how at this point in the crossover. The third part of “Crisis on Infinite Earths” airs Tuesday, Dec. 10, and the final two hours air back-to-back on Jan. 14, 2020.

The second part of this year’s “Arrowverse” crossover killed off one version of Batman: Earth-99’s Bruce Wayne (Kevin Conroy), who had given up his do-gooding — and killed that Earth’s Superman. When he turned his rage toward Kara aka Supergirl (Melissa Benoist) and infected her kryptonite, his quasi-cousin Kate aka Batwoman (Ruby Rose) set out to stop him — and accidentally killed him.

“She didn’t intentionally try to kill him,” “Batwoman” executive producer Caroline Dries explains. “He was being vicious and she was being defensive of Kara. … So she’s not going to have the weight of that on her shoulders. [But] she just looked at her future in the mirror, and is like, ’Is this who I’m going to become?’ And that’s why it’s so important that she’s establishing this relationship with Kara, who can kind of talk her off the ledge and say, ‘No, that’s not who you are.’”

But as close as Kate and Kara have gotten, the end of the episode revealed that Kate took Bruce’s kryptonite. Dries teases that move is “teeing up the third episode of the crossover and an internal conflict that Kate has.”

The second hour of the crossover also served to introduce a number of the Clark Kents from the multiverse, including versions played by “Smallville’s” Tom Welling and former big screen Man of Steel Brandon Routh. (Routh currently plays Ray aka The Atom on “DC’s Legends of Tomorrow”; but his Clark will also stick around beyond the second hour, as his Superman was deemed a Paragon who might be able to help save humanity.)

The introduction of Welling’s version of Clark also revealed a twist: This Clark gave up his powers to raise a family with his Lois (Erica Durance) and their daughters.

“We had conversations about how to best see Tom again,” Dries explains. “We knew that we really wanted Brandon Routh to be Clark Kent in the Daily Planet. Tom Welling’s Clark Kent that we all picture when we think of him is Clark on the farm. So it made sense and the farm is still there.”

The scenes filmed at the same location where “Smallville” was filmed, too. “Tom was joking when he was there, ‘Oh, that cow recognize me,’” Dries recalls. “So it all felt very 10 years ago, in a great way. And so it just felt natural.”

Guggenheim shares that Welling was excited to return to his roots with Clark but play a new version of him. “We got on the phone with him and basically pitched him everything,” he says, adding that Welling’s response was basically “I love this. … You guys have basically written the one scene that I can’t say no to.”

Looking ahead, Guggenheim adds there’s another sequence like the cameo-filled opening of “Crisis on Infinite Earths: Part One” that is “one of my favorite things.” And Barry, who has a history of accidentally changing things in an attempt to help, “will do something that is very significant that will have ramifications for the remainder of Season 6 of ‘Flash.’”