Castlevania: Resurrection was originally slated to release for the Sega Dreamcast in 1999, the same year as Castlevania 64 and Castlevania: Legacy of Darkness. After a series of delays, it was ultimately cancelled in March of 2000.
The game's plot saw the return of Sonia Belmont, the protagonist of the controversial Castlevania Legends. It seems that she had somehow been transported to the 19th century as the Belmont of the era, Victor Belmont, rejected the legacy of his family to become a gambler and “soldier of fortune.” Together, the two were meant to face off against an unnamed vampire countess, who wanted to enact revenge against the Belmont clan for the repeated destruction of her master, Lord Dracula.
No definitive reason has been given as to why Resurrection was cancelled, but it seems that its development suffered greatly due to the dev team's inexperience in making action platformer games, as well as Konami of America struggling to organize and maintain a proper workforce. The Dreamcast was also struggling to compete with other consoles on the market, and with the release of the PlayStation 2 on the horizon, it seemed unlikely that the game would perform well.
There exists several screenshots of the game, as well as some concept art and models, a video of the introductory movie that would play upon starting the game, early drafts of a few cutscenes, and even a playable demo.