Amos Diggory was a wizard who worked for the Ministry of Magic in the Department for the Regulation and Control of Magical Creatures. He was the father of Cedric Diggory, a Hufflepuff student and Hogwarts Champion in the Triwizard Tournament. Mr. Diggory is primarily characterized by his immense, often boastful pride in his son. His profound and public grief following Cedric's murder at the hands of Lord Voldemort serves as a stark and tragic illustration of the human cost of the Dark Lord's return to power.
Mr. Diggory worked at the Ministry of Magic, where he held a position within the Department for the Regulation and Control of Magical Creatures. He was a colleague of Arthur Weasley, with whom he maintained a friendly relationship. In August 1994, Mr. Diggory, along with his son Cedric, met the Weasley family, Harry Potter, and Hermione Granger on their way to the Quidditch World Cup. He enthusiastically reminded Arthur Weasley that Cedric had beaten Harry in a Quidditch match the previous year, a point he brought up with pride, though he did acknowledge the mitigating circumstances involving Dementors. Later that night, following the riot by Death Eaters, Mr. Diggory was part of the Ministry team investigating the casting of the Dark Mark. He initially accused Winky, Barty Crouch Sr.'s house-elf, of casting the spell and was instrumental in performing Prior Incantato on Harry's wand to prove his innocence. Throughout the 1994-1995 school year, Mr. Diggory was a vocal supporter of his son's participation in the Triwizard Tournament. He and his wife attended the Third Task to watch Cedric compete. Their pride turned to unimaginable horror when Harry Potter returned from the maze with Cedric's dead body. Overcome with sorrow, Mr. Diggory's anguished cries of “My boy! My son!” echoed across the grounds, and he had to be helped away from his son's body by Albus Dumbledore. The novels do not detail his life after this tragedy, though Harry often thinks of him with a mixture of pity and guilt.
In 1994, Amos Diggory was described as a man with a “rubicund, kindly face” and a “short, tufty brown beard”. His personality was generally good-natured and jovial, but it was overshadowed by his effusive and boastful pride in Cedric. While his love for his son was genuine, his tendency to compare Cedric's achievements to Harry Potter's often came across as tactless. Despite this, he was a dutiful Ministry employee with a sense of justice, as shown when he questioned Barty Crouch Sr.'s harsh dismissal of Winky. His character is ultimately defined by his role as a loving father, and his raw, devastating grief is one of the most poignant moments in the series.
As a long-standing employee of the Ministry of Magic, Mr. Diggory was a fully qualified and competent wizard.