The MacBoon clan was a wizarding family that, according to wizarding legend, once inhabited the Isle of Drear off the northern coast of Scotland. They are infamous for their violent feud with the rival McClivert clan, which resulted in the MacBoons being permanently Transfigured into monstrous, five-legged beasts known today as Quintapeds. The entire history of the clan is known only through the account provided in the textbook Fantastic Beasts and Where to Find Them.
According to legend, the Isle of Drear was once home to two wizarding clans: the MacBoons and the McCliverts. A bitter rivalry existed between the two families, which culminated in a drunken duel between their respective heads, Quintius MacBoon and Dugald McClivert. The duel ended with the death of Dugald. (Fantastic Beasts and Where to Find Them) In an act of terrible revenge, a group of McCliverts surrounded the MacBoon family dwellings one night and used Transfiguration to transform every single MacBoon into a grotesque, five-legged creature. The McCliverts quickly discovered their fatal error. The MacBoon clan had a reputation for “spectacular incompetence at magic”, and this lack of magical aptitude somehow made the Transfiguration irreversible and the resulting creatures far more dangerous than their human forms. (Fantastic Beasts and Where to Find Them) The newly created beasts, which became known as Quintapeds, resisted all attempts to be turned back into humans. They proceeded to attack and kill every last member of the McClivert clan on the island, leaving the Isle of Drear populated only by themselves. To this day, the Ministry of Magic, through its Department for the Regulation and Control of Magical Creatures, has been unable to capture a specimen to attempt to reverse the Transfiguration. The Isle of Drear was subsequently made Unplottable to protect the outside world from these dangerous creatures. (Fantastic Beasts and Where to Find Them)
No description of the MacBoons in their human form exists. Following their Transfiguration, they took on the appearance of the Quintaped: a low-slung body with five legs, each ending in a clubfoot, and covered in thick, reddish-brown hair. (Fantastic Beasts and Where to Find Them) In terms of personality, the clan was known for being spectacularly inept at magic while human. After their transformation, they became highly aggressive, carnivorous, and demonstrated a particular taste for humans. The fact that they have resisted every attempt by the Ministry of Magic to be Untransfigured has led to the assumption that they are content to live out their lives as beasts. (Fantastic Beasts and Where to Find Them)
The defining characteristic of the MacBoon clan's magical ability was its profound lack. They were known to be “spectacularly incompetent at magic”. This incompetence ironically played a key role in their legend, as it is believed to be the reason the Transfiguration performed on them was both irreversible and resulted in them becoming exceptionally dangerous creatures. (Fantastic Beasts and Where to Find Them)
The only known possessions of the MacBoon clan were their dwellings on the Isle of Drear. These homes were the site of the McCliverts' retaliatory attack. (Fantastic Beasts and Where to Find Them)
The story of the MacBoon clan does not appear in the original seven *Harry Potter* novels. All known information comes from the supplementary textbook Fantastic Beasts and Where to Find Them, written by J.K. Rowling under the pseudonym of Newt Scamander. Within that text, the story is presented as a “legend,” meaning its absolute factual accuracy within the Wizarding World is not guaranteed.