Grimoire Heart was one of the top three Dark Guilds that the Balam Alliance is comprised of, as well as the one commonly considered the strongest Dark Guild.
The guild owes its name to the Devil's Heart, an organic device which is the source of Guild Master, Hades' immense power, kept inside the guild's airship. When Grimiore Heart first rumored to have any stable location.
Grimoire Heart's strength lowered significantly: three of their top members, including Hades himself, were killed, one was turned into trees, and two (technically three, seeing as Caprico was being possessed by Zoldeo) of them defected from the guild. Following Tenrou Island's destruction at the hands of Acnologia, Grimoire Heart had disbanded all together.
Following the defeat of Grimoire Heart and Acnologia's destruction of Tenrou Island, the surviving members had gone missing. Even after seven years have last, the current whereabouts and the statuses of the surviving members of Grimoire Heart remain unknown. The only exception is that of Rustyrose who seeks to revive the guild (though that's anime exclusive).
The guild is the main puppeteer behind some events of the manga.
- Puherito, in an attempt to revive Mavis, created Fairy Heart, the unlimited source of magic that caused a global war between the continents of Ishgar and Alakitasia many years later.
- Puherito also abandoned a newborn August (the son of Mavis and Zeref ), indirectly helping to direct him to the chain of events that eventually led him to become one of the Spriggan 12 of Alvaraz alongside his father.
- After leaving Fairy Tail and being immersed in the practices of black magic, Puherito adopted the name of Hades and was bribed by the idea of looking for keys to Zeref's awakening to create a world of magicians. All of which led him to create Grimoire Heart and unleash a series of events that eventually led to the war between the dark guild and Fairy Tail guild.
- Zoldeo killed the Brandish μ's mother, this caused Brandish a desire to take revenge on Layla Heartfilia erroneously (believing she was the culprit) and her daughter Lucy. This fact is also one of the consequences that led the girl to enlist in the Alvarez Empire and become one of the Spriggan 12.
- Ultear has corrupted Jellal's mind and manipulated it for many years, which in the long run led to the events of the Tower of Heaven.
- Ultear, under the guise of Zalty, was also the mind behind the crazy plan of Lyon Vastia to awaken Deliora .
- Both Ultear and Jellal (under the false identity of the his alleged twin Siegrain) have infiltrated the Council of Magic headquarters, climbing their social position to become 2 of the supreme leaders.
At the same time, some former members of the guild also helped to make a significant contribution to saving the situation when everything seemed lost.
- Ultear and Meredy, with Jellal, founded the Crime Sorcière guild to make amends withtheir criminal past by chasing Zeref and the other dark guilds.
- During the events of the Eclipse portal, Ultear, devoured by guilt, decided to atone for her sins trying to bring back the time at least a moment before opening the portal through the Last Ages spell. In doing so, she had to sacrifice almost all her time aging prematurely and, although she managed to move the world's hands of time back a minute, she managed to save the lives of many magicians and to overturn the clash between the 7 dragons and humans in favor of this last.
- While all Dragon Slayers had been catapulted into the Space between Time to fight the human form of Acnologia and the dragon form started to unleash chaos, Meredy helped Lucy Heartfilia to accumulate enough Magic Power to imprison the dragon inside the Fairy Sphere's spell by linking the girl to all the living beings who, at that moment, were on the continent of Ishgar.