|A book describing how the mighty among summoners can bend to their will the terrible things from betwixt the planes. Many have been the unwary souls, however, who have toyed with this tome and been driven mad by unimaginable eldritch horrors.|
|a - Malign Gateway||Summoning/Translocation||7|
|b - Summon Horrible Things||Summoning||8|
- Prior to 0.27, this book contained Monstrous Menagerie and Summon Greater Demon. Also, it was one of a few "special books" that could not be gifted by Sif Muna.
- Prior to 0.17, reading the Grand Grimoire required you to have both level 6 in Spellcasting and level 10 in Summonings. It also contained Aura of Abjuration instead of Monstrous Menagerie.
- Prior to 0.16, this book contained Haunt and Forceful Dismissal.
- Prior to 0.14, the Grand Grimoire contained Mass Abjuration instead of Aura of Abjuration, and Demonic Horde instead of Forceful Dismissal.
- Prior to 0.12, failing to memorise a spell from this book could produce severe Summoning miscast effects. The Grand Grimoire was one of the books gifted by Vehumet. The followers of this god were able to read this book without the required amounts of Spellcasting and Summoning.
- Prior to 0.8, this book was called the Book of Demonology, and contained Call Imp, Abjuration, Recall, and Summon Demon instead of Haunt and Malign Gateway.