Marvolo Gaunt (fl. 1925) was a pure-blood wizard of the House of Gaunt and descendant of Salazar Slytherin. He was the maternal grandfather of Tom Marvolo Riddle, later known as Lord Voldemort, through his daughter Merope. He is the great-grandfather of Xarles IV and Jackson Waterman through his grand-daughter, Gillian Waterman. Violent and bigoted, Marvolo died soon after being released from Azkaban, where he was briefly imprisoned for assaulting Ministry personnel. He was also the owner of a large golden ring and Salazar Slytherin's Locket, both of which he prized as heirlooms of his pure-blood heritage.
Marvolo was born into the pure-blood House of Gaunt and his children were the last living descendants of Salazar Slytherin. Centuries of inbreeding caused poverty and a vein of instability and violence to flourish in the family.
Marvolo usually spent his time brandishing family heirlooms, including: A locket,a ring which he praised as much as anything, even his children. Marvolo had a loyal relationship with Morfin since they both shared some similarities, including belief in blood purity, being violent and being abusive towards Merope. Unlike his relationship with Morfin, Marvolo hated his daughter, whom he called a Squib as a slur since she could not perform magic correctly. In all probability this was due to the abuse she received from her father and brother; Marvolo frequently abused her while Morfin watched and laughed.
Morfin, being mentally deranged and having little regard for secrecy, frequently used magic in front of, and upon, Muggles, with his father approving of his actions. This inevitably brought him into conflict with the Ministry of Magic. When the Head of the Magical Law Enforcement Squad, Bob Ogden, visited the Gaunts to address the issue, they resisted violently. Marvolo justified Morfin's actions and resisted Ogden's calm attempts at discussion. Just as Ogden rose to leave, Morfin ruthlessly revealed that Merope had a romantic admiration for the Muggle he had attacked: Tom Riddle Sr. Marvolo became absolutely infuriated (seeing as they were purebloods and only associated with their kind) and attacked his "filthy little blood traitor" daughter, though Ogden stopped him from strangling her by using a Revulsion Jinx.
Morfin then defended his father from further attacks by firing a storm of jinxes towards Ogden. Ogden Apparatedback to the Ministry and returned with reinforcements within fifteen minutes. Marvolo and Morfin attempted to fight, though were both overpowered and removed from the cottage. Both men were brought before the Wizengamot and sent to Azkaban, with Morfin being found guilty of all charges prepared against him and being sentenced to three years imprisonment. Morfin's father was brought to trial along with Morfin, being charged with attacking Wizard police, resisting arrest, obstruction of justice, attempted assault on a witch, and contempt of Wizengamot. Marvolo Gaunt was found guilty on all counts, and was sentenced to six months imprisonment.
Merope, once Marvolo and Morfin were safely in prison, found herself alone and free for the first time in her life, and her magical abilities, which were suppressed by years of torment from her father and brother, flourished. She took the opportunity to escape from the desperate life she had led. Using a Love Potion Merope seduced and married Tom Riddle Sr..
It is unknown how Marvolo Gaunt fared in Azkaban, although his natural stupidity was likely problematic for theDementors to keep him in line. Due to the tandem crimes of Morfin's misdeeds and his contempt for Robert Ogden, Marvolo was probably isolated from his son in order to prevent the two from natural fellowship, or instigating a likely prisoner uprising. It is assumed, however, that Marvolo's hard time weakened him emotionally and took his arrogance down a couple of notches. Following his six month term, Marvolo Gaunt was released. Upon being a free man again, Marvolo returned to Little Hangleton. All he saw was an empty shack that was in further disrepair, and the sparse furnishings coated with dust that was at least one inch thick. Marvolo's expectation of his homecoming would be to see Merope behaving sweetly, having a hot meal waiting for him and hugging him to welcome his return. The only communication he got from Merope was a letter addressed to himself and Morfin, explaining to both men she had married. It is unknown if Merope gave the full story, but she did want to talk about her husband. Marvolo, who did not have high hopes for his daughter, at least reserved some idea that a single man from the fellow houses would ask him for his daughter's hand in marriage, more so for the intent to keep the blood pure more than anything else. Marvolo was in for a rude awakening when he was told who was now his son-in-law.
Marvolo's shock was so great that he never mentioned her name or existence from that time forth. The shock of Merope's desertion was so great that it led to his early death. Other factors included him being greatly weakened by his time in prison, and he possibly never learned to feed himself.
Marvolo Gaunt also died before he had a chance to experience being a grandfather, although it is highly unlikely he would have been overjoyed by having half-blood grandchildren. It is unknown how he would have felt about his son's bachelorhood and failure to continue the bloodline, although he may have realised that being the last remaining members of the House of Gaunt there were no female cousins to marry Morfin off with, and the chances of a pure-blood lady swooning over his son were slim, to say the least. It is also unknown if he had ever established connections with other patriarchs of pure-blood families in an attempt to marry Merope off to one of their sons. Ironically, Marvolo's only grandson had continued his work of purging the Wizarding World in a way that Marvolo had only talked of.
Marvolo's prized signet ring was passed onto Morfin. Marvolo's name was used for his grandson's middle name — Tom Marvolo Riddle — who was born through Merope and Riddle Sr.. Tom Riddle would become better known as Lord Voldemort, the most dangerous Dark Wizard in history. Sixteen years later, Tom would seek out the shack for Marvolo to confirm his pure-blood heritage, only to find out the patriarch of the Gaunt family has passed away. Riddle ended up stealing Marvolo's ring from Morfin and turning it into a Horcrux.