In spite of the all new magical creatures coming to The CW's superhero team-up drama this season, executive producer Phil Klemmer reveals to THR that the new big bad is "everyday evil and institutional evil ... people who are good and take a turn for the sinister."

Welcome back to The Hollywood Reporter's weekly DC TV Watch, a rundown of all things DC Comics on the small screen. Every Saturday, we round up the major twists, epic fights, new mysteries and anything else that goes down on The CW's Arrow, The Flash, Legends of Tomorrow, Supergirl and Black Lightning, and Fox's Gotham. The new seasons of all the Arrow-verse series are (finally!) almost here, so this week let's take a deep dive into what awaits in Legends of Tomorrow season four ...

Key changes: Keiynan Lonsdale has officially left the series, and Matt Ryan joins as series regular to fill the void along with Ramona Young as new Legends team members aboard the Waverider. However, Ryan's John Constantine does not join the team immediately, and that's for a very specific reason.

"The reason we held back on making him a Legend is we always wanted to keep that shroud of mystery around him," executive producer Phil Klemmer tells The Hollywood Reporter. "We didn't want to have him acclimate ever to being integrated with the team." Because the groundwork for the character was laid on NBC's original canceled series, the Legends of Tomorrow showrunner "selfishly wanted to create some new mystery around him for our show."

"So between dropping off the dragon's head and knocking on Sara [Caity Lotz] and Ava's [Jes Macallan] door in the middle of the night in the premiere, he lived a very eventful five months," Klemmer adds. "He was in a pretty good spot, relatively for Constantine, but we wanted him to be darker, more troubled, more mysterious. That's something for the audience to have to unravel: What happened to Constantine during the offseason and why has he changed?"

Larger theme: Season four is making the push to focus on magic and mysticism with the addition of Constantine. But the new overall theme had an unintentional affect on the Arrow-verse's lightest and most comedic series.

"Ironically it made it much darker," Klemmer says. "It made it much more morally ambiguous. When you're trying to fix history, you can argue about how it needs to be done but you have to fix it. With magical creatures, you're asking big questions like do they belong in our world? Is this really our world to police? We spent a ridiculous amount of time debating morality for a show that's a time-traveling action comedy. Is it fair to put a Minotaur in a cage at the Time Bureau? None of these things exist, but we're asking if a Minotaur has a soul and conscience."

In the cases-of-the-week, the Legends (and audience) will discover that everything they think they know about magical creatures and monsters is wrong. "We are far more interested in finding a nuance in these monsters and turning myths and legends on their heads," Klemmer adds. "We are finding out what fairytales got wrong about various magical creatures and monsters. Some of the ones that are supposed to be magical are murderous and vice versa."

New villain: With the focus on magical creatures and monsters this season, one would expect the season-long villain to be of magical origin. But Legends of Tomorrow is flipping the script again for this year's big bad.

"We were really interested in seeing how human beings without super powers react to this onslaught of magical beings," Klemmer says. "So we wanted to find everyday evil and institutional evil, looking at people who are good and take a turn for the sinister. The magical creatures are so crazy and over the top that we wanted to make our big bad a little more human-scaled. I'm talking a little bit around the punchline here – we've seen doppelgangers but we've never had the Legends fracture as a group. We wanted to challenge those kinds of bonds this season."

New main character: Maisie Richardson-Sellers is hanging up her Vixen uniform for the last time to take on a new character as she remains a series regular on the show.

"She is one of these supernatural creatures, so she's 'one of the enemy' and yet becomes a member of our team," Klemmer reveals. "The definition of enemy really gets turned on its head because of her this season. We knew we wanted to give her something new to do, and episode 3 is our punk rock, London, '70s episode and when we'll explain it all. Amaya was so stayed and buttoned-up and proper, and we could feel that Maisie was champing at the bit to do something else. Her whole physicality has changed into something totally different."

The crossover: Legends of Tomorrow is sitting out of the big Arrow-verse crossover this year as for the first time ever, not every series is included. What does it mean for future crossover events?

"I don't know. People are already talking about crossover 2019. We're on standby," Klemmer says. "I don't know how that will work. There's already a loose shape for it even though this year's crossover isn't done by a long shot. I was happy to have sit this year out just because we only have 16 and our run of episodes was so tight and integrated. It's always a blast but it is a departure. I'm glad we got to do a straight run this year."

The future: Legends of Tomorrow has finally found its footing as the most meta, wacky and self-aware superhero series in the Arrow-verse. But it took three seasons to get here. What will this show look like after another year of evolution and finding itself?

"We have settled into this weird life cycle where things get way too complicated and then we simplify things only to then complicate them again," Klemmer says. "We get to a point where we're like, 'Things got a little out of control there, it worked, we took big swings but it's time to tighten up.' But we just can't help it – it's hard to restrict ourselves with our roster of Legends, the ability to go anywhere in time, tell almost any genre of story. So I can't predict what exact direction we'll go in the future but it's pretty obvious that it's going to be much different a year from now or two years from now."

He continues, "We virtually change genres over the course of four seasons but the one-hour comedy is something I have always loved doing and the fact that this show organically turned into one really surprised me. Maybe we'll go back to being a hard-core, super serious, straight CBS procedural by the time we get to season six. Nobody is making demands of us, nobody is saying no to us, studio or network, so we're willfully wacky, odd and out-of-step with everything else on TV."

Fun fact: Heat Wave (Dominic Purcell) isn't done writing his book. "You'll get to see Mick Rory leaning in to his secret literary career," Klemmer teases with a laugh.

Legends of Tomorrow season four premieres Monday, Oct. 22, on The CW.