Darkhold

: "The Darkhold."
: "You're familiar with the Darkhold?"
: "I know it's the Book of the Damned, and that it corrupts everything and everyone that it touches."
: ―Stephen Strange and Scarlet Witch[src]
The Darkhold, also known as the Book of Sins, the Book of Spells, or the Book of the Damned, was a book of spells created by Chthon.
For years many people tried to find the Darkhold, including Johann Schmidt and Nick Fury. It was finally found by Joseph and Lucy Bauer, although the Darkhold corrupted them along with Eli Morrow, who tried to kill his co-workers to take the book for himself. In 2017, after Morrow's demise, the book was used by Aida and Holden Radcliffe to upgrade the Framework virtual reality, which was used to trap several S.H.I.E.L.D. agents. Aida used the Darkhold to create herself a human body using dark matter, pitting her against Ghost Rider, who helped S.H.I.E.L.D. defeat her before taking the book back to the Dark Dimension.
The Darkhold was retrieved by Morgan le Fay in an attempt to merge the Dark Dimension with Earth. However, she was stopped by the Runaways and PRIDE, who used the book to imprison her in the Dark Dimension.
The book was then obtained by Agatha Harkness, who brought it with her to Westview in order to amplify her powers so she could manipulate the Westview Anomaly without being noticed. It was later taken by Scarlet Witch, who read it, although the book corrupted her into unleashing a rampage to gain alternate versions of her children. However, as soon as she broke out of its influence, she destroyed every copy of the Darkhold within the Multiverse to stop it from being misused.
*Credit for this page comes from here: https://marvelcinematicuniverse.fandom.com/wiki/Darkhold)