Osgood Oswald Vance, commonly known simply as 'Vance', a character in The Repairer of Reputations.
His father is president of Seaforth National Bank, although he secured his present position as a bank cashier through his influential uncle. Vance had been in Sing Sing for forgery before being transfer to the Asylum for Criminal Insane - it seems that some time prior to being sent to the latter he was exposed to The King In Yellow.
On 19th January, 1918, Vance was pardoned by the Governor of New York.
Since 20th March, 1919, Vance has been embezzling money from the bank, amounting to $20,000 by the time of the story.
On 28th April (1919? 1920?), Vance called Mr. Wilde to have his reputation repaired. His reputation had been damaged at Sheepshead Bay, where it had been suggested that he was living beyond his means.
Mr. Wilde and Hildred Castaigne outline the plan they have need of Vance to carry out. Although not initially clear to the reader what this plan is it becomes clearer when Wilde indicates Hildred as "the cousin of the King!" Hildred goes on to explain that his cousin Louis Castaigne must never marry, that he must be exiled or killed. Mr. Wilde then presents further details by sketching a plan of Hawberk's rooms, where presumably the old man and his daughter live.
Prior to his supposed death, when he runs past Hildred Castaigne and his cousin into a Lethal Chamber, Hildred deduced that Hawberk and his daughter are dead and Louis is no longer a threat. This is proved wrong when they are seen alive shortly after. It is unclear therefore why he has committed suicide. Perhaps he was unable to murder Constance and her father and wishes to end Mr.Wilde's control over him.
Mr. Wilde dies shortly after Vance runs into the Lethal Chamber, his throat torn out. Did Vance have any hand in this?
It is also possible that Vance was sent to kill Doctor Archer, if Hildred did not kill him himself.
The version of Vance in the Trail of Cthulhu adventure based on The Repairer of Reputations is outwardly very similar, spending beyond his means and gambling at the Sheepshead Bay racetrack. The one obvious difference is that it is claimed it is his uncle that is the president of Seaforth National Bank. Additionally the whole flow of the story assumes that Vance commits suicide without any further story elements coinciding with it, such as the death of Mr. Wilde, or the dragging away of Hildred Castaigne to a mad house.