WARNING: The following contains major spoilers for The Conjuring: The Devil Made Me Do It, now in theaters and on HBO Max.
In the Conjuring Universe, most of the enemies that Ed (Patrick Wilson) and Lorraine Warren (Vera Farmiga) face are spiritual in origin. However, in The Conjuring: The Devil Made Me Do It, the couple encounters a pair of antagonists that are unlike anything they have ever fought before. Not only are they humans with skills similar to their own, but their motivations also make them the perfect antithesis to the paranormal investigators.
For years, the Warrens have helped others through exorcisms, hauntings, and curses in the most recent film's case. However, of all of the demonic entities they have faced, they've yet to encounter anyone similar to them until now. Father Kastner (John Noble) is a priest with a deep understanding of the occult, specifically the Disciples of the Ram. The cult in question mainly operates to worship the demon that now possesses the Annabelle doll. In between his studies, he fathered a daughter, Isla (Eugenie Bondurant), whose curiosities would get the better of her and lead her down a path to being one of the strongest cult members.
Like Ed, Father Kastner has no spiritual or psychic gifts. However, he makes up for it with keen intelligence and encyclopedic knowledge of the occult. He also has an obsessive personality when it comes to understanding the cult, a quality shared with Ed, who can dive headfirst into a case when needed. This was how he pinpointed the Occultist's location. While Father Kastner isn't inherently evil, his lack of effort to stop his daughter places the Warrens in life-threatening situations.
Isla shares nearly identical abilities to Lorraine, who uses her powers to commune with spirits and help those in need. But Isla uses her abilities to summon and control demons and create curses through satanic rituals. Another thing that makes the pair two sides of the same coin is how Lorraine organically uses her powers and is weakened by them, where Isla borrows these abilities through witchcraft at the cost of her own soul. The two each give a part of themselves to do their work, but the latter is far more selfish.
When it comes to how each pair gains their strength, the Warrens focus on their love for one another. Toward the end of The Conjuring: The Devil Made Me Do It, Ed is tricked into attempting to kill his wife through a strange powder, but it's the love they have for one another that helps him overcome his influence and save his wife. In contrast, Isla gains power through her twisted rituals. As a result, she has no compassion for anyone close to her. This mindset is why it was so easy for her to kill her father after he guided Lorraine to the altar.
Father Kastner and Isla are by no means the perfect pair, especially when compared to Ed and Lorraine. But the way the two operate and how they gain strength makes them the perfect antithesis to the paranormal investigators. To further show how similar, yet different, the pairs are, Kastner has his own basement filled with occult items the same as the Warrens. Ultimately, the villains represent how any bad decision in the Warrens' life could have sent them down a similar path.
Directed by Michael Chaves, The Conjuring: The Devil Made Me Do It stars Patrick Wilson, Vera Farmiga, Ruairi O'Connor, Sarah Catherine Hook and Julian Hilliard. The film is now in theaters and on HBO Max.