Great-Aunt Muriel is a centenarian pure-blood witch and the great-aunt of Molly Weasley (née Prewett) and her brothers, Gideon and Fabian Prewett. Known for her extremely sharp tongue, love of gossip, and judgmental nature, she is a formidable presence at any social gathering. Despite her often-unpleasant demeanor, she proves her underlying loyalty to her family and the anti-Voldemort cause by providing her home as a safe house for members of the Order of the Phoenix and the Weasley family during the height of the Second Wizarding War.
Muriel was at least 107 years old by 1997, indicating she was born no later than 1890. In her youth, she was acquainted with a young Albus Dumbledore, whom she recalls dancing with at her cousin's wedding, and was privy to the local gossip surrounding the Dumbledore family in Godric's Hollow, particularly concerning Ariana Dumbledore's health and Kendra Dumbledore's secrecy. Her long life gave her a vast repository of wizarding society gossip, which she eagerly shared with anyone who would listen, including the journalist Rita Skeeter for her scandalous biography, The Life and Lies of Albus Dumbledore. Her most prominent appearance occurs at the wedding of her great-great-nephew Bill Weasley to Fleur Delacour at The Burrow. Throughout the event, she offers a running commentary of criticism, disparaging Fleur's dress, Ginny Weasley's attire, and the unconventional appearance of Xenophilius Lovegood. She engages in a heated, gossipy argument with Elphias Doge regarding Dumbledore's past, championing the scandalous version of events published by Rita Skeeter. Following the fall of the Ministry of Magic and the increased danger to blood traitors, Arthur Weasley placed Muriel's home under the Fidelius Charm. Her house subsequently became a safe haven for the extended Weasley family and other allies. Though she complained endlessly about the number of people crammed into her home, her willingness to provide shelter was a crucial act of defiance against the Death Eaters.
Muriel is described as a small, stooped old witch with a “face like a shrunken head” and a “vulture-like neck.” She wears a cloudy, walnut-coloured wig and, at Bill and Fleur's wedding, a large, feathery pink hat. Her personality is defined by her cantankerous, abrasive, and brutally honest nature. She is an unabashed gossip who seems to delight in the scandals and shortcomings of others. She is highly critical and vocal about her opinions, regardless of who she might offend. However, beneath this crotchety exterior lies a core of loyalty. Her decision to host the Weasleys in her home demonstrates a grudging but firm allegiance to her family and the right side of the war.
As a witch who lived to be well over one hundred, Muriel was presumably a competent and knowledgeable magic-user. However, no specific magical feats or skills are detailed in the novels. Her primary contribution to the war effort was non-combative, offering her protected home as a sanctuary.
Muriel's relationships are primarily familial. As Molly Weasley's great-aunt from the Prewett family, she views the Weasley family with a critical eye, particularly Arthur Weasley's interest in Muggles, but is ultimately a family member they can count on in a time of crisis. Her interactions with Elphias Doge at the wedding showcase her love for contentious debate and gossip, especially when it concerns figures as renowned as Albus Dumbledore. She was also a key informant for Rita Skeeter, demonstrating her central role in the upper echelons of wizarding society's rumor mill.
Great-Aunt Muriel is completely absent from the film adaptations. Her role in providing commentary and historical gossip about Dumbledore at the wedding in Harry Potter and the Deathly Hallows – Part 1 is cut, and her home is never mentioned as a safe house (film).