Diana Alecto Grimm is a Special Inquisitor with the Office of Special Inquisitions (part of the Wizard Justice Department), and one of the Grimm Triples, being the older sister of Lilith and Hecate Grimm. Her Animagus form is that of "a large black owl."
On 25 March 1996, Diana conducted an interview with Claudia Quick concerning the paternity of Alexandra Quick, based on the belief that the child's father was a Dark Wizard connected with the Thorn Circle and the Dark Convention. After finding that Claudia knew nothing of Alex's father, Diana Obliviated Claudia, filing a report with the Territorial Census Office in Chicago, Illinois.
In August 2008, Diana met Alexandra at the Larkin Mills Mall when she enchanted a store mannequin to scare off Billy Boggleston's friend Tom Gavin, who had attempted to steal Alex's bookbag. She then took Alex to lunch, inquired after her father, and gave her a business card to replace the one given her by Governor-General Hucksteen the previous June, which Alex had burned.