Justin Baldoni, Wayfarer Studios Sue Blake Lively, Ryan Reynolds and Publicist

Justin Baldoni is continuing his legal crusade against his "It Ends With Us" costar Blake Lively -- he and his production company just filed a massive lawsuit against Blake, her husband Ryan Reynolds and her publicist Leslie Sloane ... seeking hundreds of millions of dollars.

Justin and his company, Wayfarer Studios, which produced "It Ends With Us," filed the federal suit ripping Blake and Leslie for their alleged campaign to smear Baldoni and snatch away control of the movie ... which he directed and costarred in with Blake.

According to the docs, obtained by TMZ, Blake was "determined to make Baldoni the real-life villain in her story" to deflect from getting publicly trashed as "tone-deaf" during the film's media tour.

Justin says she was promoting her haircare and alcohol line while promoting a film about domestic violence.

In the suit, Justin says the war between himself and Blake really started back in May 2023 when they started shooting the movie. He claims she was organizing a "takeover strategy" as they battled for creative control.

Justin also calls out Blake's husband for getting involved in the writing of the script. He says Blake had done a rewrite of the film's critical rooftop scene where the main characters meet, and they had a meeting at Blake and Ryan's NYC penthouse to discuss it -- but he now feels it was more of an ambush.

Justin says Ryan was there from the start, singing the praises of Blake's rewrite, and then hours later ... Blake's pal Taylor Swift popped in with her 2 cents, also applauding Blake's version of the scene.

We should note Taylor is not being sued -- she's only mentioned in passing in the suit, but Justin says he "understood the subtext: he needed to comply with Lively's direction for the script."

So, he later texted Blake to say he liked what she'd written and would've felt that way even without Ryan input.

BTW, he's included their texts in the suit, and in one, Blake describes her Taylor and Ryan with a "Game of Thrones" reference -- "I'm Khaleesi, and like her, I happen to have a few dragons ... we all benefit from those gorgeous monsters of mine."

The docs also include emails between the 2 actors from right before filming began, and Justin claims Blake "expressed warm gratitude" for all the work they'd done to prepare -- but he also believes it was all a facade, so she could wrestle away control from him.

Some of their early battles were about her character's wardrobe -- she wanted rich and sexy, but he pointed out she's playing a struggling small biz owner.

He also claims Blake hadn't read the book when they were working on the script, adding ... "she even tried to Google the color of her character's hair rather than pick up the book."

Justin also lays out his take on the controversial and heated January 2024 meeting between himself, Blake, Ryan and several other cast and crew members. He says Blake came armed with a "17-point return to production demand" ... as they were preparing for re-shoots on the film. This is the meeting when Ryan allegedly went off on Justin for the alleged sexual harassment that went on during filming.

Justin's description is pretty colorful, saying "Blake unleashed Reynolds on Baldoni and Wayfarer." He claims, although he gave in to most of Blake's demands, she continued to threaten to torpedo the movie unless she got to cut her own version of the film.

Sony Studios, the film's distributor, told Wayfarer Blake refused to promote the movie, unless they allowed her to do her own cut -- so, they made it a competition. Justin says both his version and Blake's would be shown to an audience, and whichever tested better ... would be the final cut.

Baldoni says his version "scored significantly higher with key audience demographics" -- but he claims "not surprisingly" Blake reneged on her promise, and insisted Sony release her version ... which it did. Justin says he essentially was forced to fire himself from directing the movie.

Even after all that capitulation, he claims the pressure and smearing continued ... as the movie was rolled out, all of the cast unfollowed Baldoni on social media, and backed Blake.

Justin says this is where Blake's PR team, led by Leslie Sloane, kicked into high gear with a "campaign to frame [Blake] as a martyr and pin the blame" on Baldoni. He says Sloane teamed up with his ex-publicist -- who he'd recently fired -- and mined her company phone for a slew of texts they used to "concoct a false narrative" about Baldoni.

The suit includes a ton of texts Sloane sent to various media outlets, including TMZ, in which she allegedly tried to "divert attention from Lively's tyrannical behavior on set."

BTW, the California wildfires even get a mention in the 179-page lawsuit. Baldoni says although Blake filed her legal action against him in late December -- on the "eve of the winter holidays," as he put it ... she waited several weeks to serve the papers, eventually doing so on the very day the fire exploded on Pacific Palisades.

He says while everyone was gathering belongings and watching for evacuation orders, "Lively -- from the safety of her penthouse in New York -- deployed process servers in the midst of these troubling times."

The suit -- for defamation, civil extortion, interference with contractual relations and slew of other allegations -- is seeking no less than $400 million in damages from Lively, Reynolds and Sloane.

In a statement, publicists named in the Lively lawsuit tell TMZ ... "It is devastating that we are forced to answer this viciously selfish ongoing litigation littered with documented and provable lies in the midst of the tragedy impacting California where we reside."

They say Lively's promotion of the movie "caused instant negative and organic backlash due to her own highly publicized actions" ... and they say she's blaming them.

"Over the last month we have received death threats, abhorrent abuse and vile anti-semitic slurs hurled at us due to her decision to use us as scapegoats for her own choices promoting her film in which she made millions of dollars. With this filing, we lift our own curtain of what happens when the entitled weaponize power, fear and money to destroy, intimidate and bully those who get in their way."

As we reported, Baldoni is also suing The New York Times for $250 million over the newspaper's bombshell article alleging he and others coordinated a smear campaign against Blake.