|Death||Died in the beginning of Witches Abroad|
A Fairy Godmother, completely blind but blessed with second sight - which allowed her to prepare for her impending death, including the preparation of a special package, and lying down in her own coffin, in her burial mound, waiting for Death to claim her. Just before her death, Lilith de Tempscire paid her a visit through her mirror, taunting Desiderata while Desiderata patiently went along, before covering her mirror with a cloth. In "Witches Abroad", it was mentioned that, due to the magical nature of her position, she was one of the few witches to use magic for household chores, including the laundry doing itself.
After her death, she had her Fairy Godmothering wand delivered to Magrat Garlick, thus leaving her as her apparent heir to the position, owing to her never having trained an actual heir during her life. Magrat was probably left the wand because Desiderata, like Magrat, was a research witch who owned lots of books, and because Magrat often visited her, unlike the other witches. Her handwriting was described as very neat, and she had many books filled, because of the traveling responsibility of her position.
As a Fairy Godmother she watched over Ella Saturday in Genua.
The covering-the-mirror-with-a-cloth bit is reminiscent of Gandalf covering the Palantír.
Her first name is an echo of Desiderata, a poem about getting happiness in life.
As well, Desiderat is Latin for "he/she/it wishes".