Leader of the Accionites
- "Their leader was a wizard called Gideon Flatworthy, whom the Daily Prophet famously called ‘less a wizard, more a lazy walrus-like object who lies all day on a rather smelly cushion, and expects people to admire him for it’."
- —Miranda Goshawk introduces Flatworthy in her wizarding play on the Summoning Charm in Book of Spells.[src]
After learning the magical arts, he formed the Accionites, a gang of anti-muggle activists who mostly just sat around and did nothing. When they ran out of gold, instead of going to Gringotts to get more he instead summoned several valuable goblin-made artifacts. The goblins who had created them came to the Accionites' headquarters, brandishing angry swords and "baying for the Accionites' blood".
Death and post-mortem
After disapparating twice to avoid the goblins and being abandoned by his gang, he tried to summon a farm, some livestock, and a well-stocked larder. He was crushed to death by the bales of hay and cattle that landed on top of him. Experts are uncertain why he did this (they still debate about it) although the most common theory is that he became delirious from lack of food. Sometime after he died, Miranda Goshawk published his story in her Book of Spells, in a wizarding play about the Summoning Charm.
He was extremely overweight from having lain on a pile of cushions most of his adult life, and wore a golden crown with blue robes. Flatworthy also had an extremely thin moustache. 
Magical abilities and skills
- Disapparating: Flatworthy disapparated at least twice in his life, with great success, whilst being attacked by a horde of angry goblins.
- Charms: Flatworthy was an expert at the Summoning Charm, having cast it multiple times in his life (this was because he believed himself to be above lifting and carrying things non-magically).