SPOILER WARNING: Do not read if you have not yet watched James Wan’s “Malignant.”

James Wan’s newest horror film, “Malignant,” is taking the genre — and its critics — by storm.

The Warner Bros. film, which premiered on Sept. 10 in theaters and on HBO Max, shocked audiences in its third act by revealing that Madison (Annabelle Wallis) has a parasitic twin, Gabriel (voiced by Ray Chase). Gabriel has been dormant inside of Madison her whole life, but when her abusive husband smashes her head against a wall, Gabriel wakes up and is able to hijack her body to commit murders — hence, a malignant tumor.

Critics were astonished at the twist, with Variety’s Andrew Barker speaking on Wan’s construction of the gory ending. “Watching him construct a jump-scare-laden stabbing scene at this point in his career is like listening to an accomplished concert pianist toss of yet another run through ‘Für Elise’ — and his willingness to simply go for it, especially as the film careens through its ludicrously gory final act,” Barker wrote.

Not wanting to spoil the film for those who have yet to watch, the New York Times’ Jeannette Catsoulis instead vaguely hinted at the ending, writing: “Wan delivers the kind of hilariously sick climax that only a sadist would spoil. Or envisage.”

AV Club’s A.A. Dowd wrote about “Malignant” breaking through common horror tropes. “’Malignant’ has surprises up its sleeve,” Dowd wrote. “It gets nuttier and gnarlier as it goes, the script weaponizing an audience’s assumed familiarity with the haunted-house tropes Wan helped re-popularize.”

Collider senior editor Vinnie Mancuso wrote in his piece on “Malignant’s” ending that the film marks a new direction for the horror genre. “The movie is that rare original idea that audiences are going to want to discuss (see: scream about) for reasons completely unrelated to franchise potential,” Mancuso wrote. “In that way, James Wan—and, even with far fewer films to his name, Jordan Peele—is occupying the role previously held by the late, great Wes Craven, who knew better than anyone when a style or format had run its course and the entire genre needed to pivot once again.

Other critics and fans took to Twitter to voice their opinions on the film. Rotten Tomatoes critic Shannon McGrew tweeted, “#Malignant is a game-changer. Defying the boundaries of genre film, Wan has created something unique and terrifying. It’s a deranged work of art that is destined to become a cult classic. A love letter to the genre and its fans, this is Wan at his best.”

See more Twitter reactions below.