The Ildatch is a book of black magic featured in The Wishsong of Shannara . This book emerged in the Age of Faerie, long before the rise of humankind. Its story was told to Brin Ohmsford by the Druid Allanon. Allanon also told Brin that she was the only one who could destroy it.
The Ildatch was first used by the rebel Druid Brona to increase his knowledge of Old World magic. Brona was subverted by the book's dark magic and thus became the Warlock Lord. After the Warlock Lord's defeat at the hands of Shea Ohmsford, Allanon looked for the Ildatch but could not find it. Believing it destroyed when The Skull Kingdom fell, the Ildatch was left to be discovered by a band of Men. These men believed they could control the power of the Ildatch and began to learn its secrets. Like the Warlock Lord, they were unable to resist the book's dark magic and thus became the Mord Wraiths. After they succumbed to the book's subversion, they took it deep into the Eastland and hid it within the Maelmord.
When Brin came to destroy the Ildatch, she, too, was subverted by it and was transformed. Her brother, Jair Ohmsford, then found her in a tower in the middle of the Maelmord. There, after a confrontation between subverted sister and determined brother, Brin was able to destroy it with her wishsong.
One page, however, survived, as later described in the short story "Indomitable". Cogline, Kimber Boh and Jair Ohmsford setting out to destroy the one page that survived.
The Ildatch claims that it was once part of The Word, a collection of secrets that gradually separated from it in time.