Following Daredevil's cameo in "Spider-Man: No Way Home" and Kingpin's in "Hawkeye," Marvel's Netflix series now firmly exist within the MCU canon, but the same can't be said for other projects, like the ABC series and various Spider-Man-adjacent Sony films. However, thanks to a series of subtle connections, at least one series, "Agents of S.H.I.E.L.D.," has another link to the MCU — one that may place the blame for the events of "WandaVision" on the shoulders of the Masters of the Mystic Arts.
The chain of connection runs like this: in "Doctor Strange," the Kamar-Taj library plays an important role, keeping mystical knowledge (i.e. spells) centralized and safe. But, as fans noted, the library's collection had one clear absence, suggesting a lost or stolen book. Then, in "Agents of S.H.I.E.L.D.," the famous grimoire known as the Darkhold appeared, which one of the show's EP's said, "feels like it belongs in the library in Kathmandu," i.e. the Kamar-Taj library. The Darkhold then reappeared in "WandaVision," amplifying the powers of Agatha Harkness. Referring to the two series' Darkholds, "WandaVision" director Matt Shakman said that he "would imagine it's the same book."
In the eyes of key creatives behind the shows, then, the Darkhold that Harkness used to manipulate Wanda in the MCU's "WandaVision" is likely the same magic tome that was stolen from the watchful eyes of librarian Wong and the Masters of the Mystic Arts back in "Doctor Strange."
