WARNING: The following contains spoilers for WandaVision Episode 9, "The Series Finale," now streaming on Disney+.

Officially, WandaVision introduced the Darkhold to the Marvel Cinematic Universe proper. While a version of the book first appeared in Marvel's Agents of S.H.I.E.L.D., it finally appeared in its true form in the season finale of WandaVision. In the last two episodes of WandaVision, Agatha Harkness revealed her true self, and in the finale, she explained the powerful dark magic of the Darkhold to Wanda Maximoff, who studies the book in the post-credit scene of the final episode, becoming an even more powerful witch.

While the Darkhold has touched the lives of many Marvel magic users, it was originally introduced through a story involving Werewolf by Night, the first Marvel character Moon Knight ever fought.

The Darkhold's first appearance was in 1971's Marvel Spotlight #4 by Gerry Conway, Mike Plogg & Sam Rosen. This was a Werewolf by Night story -- starring Jack Russell as the supernatural antihero -- where it turned out that it was Jack Russell's late father who once owned the book. His father was Gregor Russoff, a Transylvania nobleman and werewolf who was killed by a silver bullet. In this story, a reporter named Buck Cowan shows up and told him the Darkhold was in his father's old castle, which had since been sold to Dr. Miles Blaskgar.

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Werewolf by Night Darkhold

According to Cowan, Jack's dad was a European warlock, and the Darkhold was his book of spells, but this turned out not to be the case. Jack found the Darkhold book in his father's old library and learned what Blaskgar wanted with the book. The man was running various experiments using spells to try to find a cure for his daughter, Marlene. She was a mutant and had a  gorgon-like power that could turn people to stone. She looked at Jack and turned him into stone in her garden. Shockingly, that was Jack's end in Marvel Spotlight, as the next issue started a running storyline with Ghost Rider.

The story continued in 1972 in Jack Russell's own series Werewolf by Night #1-3 by Gerry Conway, Mike Ploog, Frank Chiaramonte & John Costanza. When the sun rose, Jack was no longer a stone statue. He set out to find a way to transcribe the Darkhold but thought he destroyed it.

The Elder God, Chthon, wrote all of his spells in the Darkhold, a book made of indestructible parchments of flesh. He left the book on Earth to continue to spread its power and magic. Included in the book were the spells that caused lycanthropy, which is why Jack Russell's dad had it to begin with. Gregor Russoff read the spell and became a werewolf before sending his wife and son away. It was too late, as he had passed on the curse to Jack, as well as his granddaughter Nina Price.

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Gregor Russoff and the Darkhold

In 1988's X-Men Annual #12, the story "Demon Knight" by Mark Gruenwald, Ron Lim, Tony DeZuniga, Gregory Wright & Ken Lopez showed Gregor Russoff using the book. Gregor tried to free Chthon on Wundagore Mountain using spells from the Darkhold. The spell was cast when the twins, Pietro and Wanda Maximoff, were born on Wundagore Mountain. Chthon planned from the start to claim the form of one of the twins for his eventual return — the one who would one day be known as the Scarlet Witch.

With the Darkhold's power to create werewolves, it could very well show up again in some capacity in the upcoming Disney+ series Moon Knight. Moon Knight made his first appearance in 1975's Werewolf By Night #32, by Doug Moench and Don Perlinwhere he was tasked with hunting down Jack Russell. While those two heroes went their separate ways, they have crossed paths a few tomes over the years, and it wouldn't be too surprising for the mythologies to be intertwined in the MCU. And considering the fact that Jack's family was responsible for linking the Scarlet Witch to the Darkhold in comics, this could even give the MCU's Scarlet Witch a reason to pop back up in Moon Knight..

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