The Black Grimoire is a powerful spellbook filled with druidic magic.
The Loughlin Family was a family of powerful witches who once owned the Black Grimoire. Aspiring or talented witches would come from around the world to study the Black Grimoire's secrets for a price. When hunters attacked the family, three members managed to escape and took the Black Grimoire with them. The surviving three Loughlin's eventually settled in Eureka Springs, Arkansas.
In 2017, the Loughlin Family drew in the attention of Sam and Dean Winchester after they killed Barry Gilman for stealing money from them. Dean personally hunted down and killed Gideon Loughlin, but not before Gideon cast the memory curse on Dean. When Sam discovered Dean was gradually losing his memories and his identity, Sam employed Rowena to help cure Dean. They were unfortunately captured by the two remaining Loughlins', Catriona and Boyd, but Dean killed them using witch-killing bullets, rendering the Loughlin Family extinct. Rowena was then able to use the Black Grimoire to break the curse Gideon had cast on Dean.
Although Rowena intended to take the Black Grimoire with her, Sam confiscated the book but agreed that he and Dean owed her one for her help.
Although it is named the Black Grimoire, the tome itself has a dark green leather cover. It has a silvery heptagram symbol adorned on its cover, and smaller one on its side cover. Like old books, it has aging papers.
The book itself was written in Old Gaelic text. Among its contents, it featured a set of tables of Druidic glyph and pictures, which provided detailed steps for spellcasting.