The plot of Castlevania ROM series is based on eternal battle between Belmonts' clan and count Dracula. Each 100 years Dracula rises from his grave in order to drink blood of innocent people and to propagate an army of evil creatures aimed at plunging the world into darkness. And Belmonts possessing special vampire killing power have to interfere with treacherous Dracula's plans.
One of the most remarkable Belmonts is Simon Belmont - the main character of the two earliest Castlevania games. However not only Belmonts are able to fight vampires. One of such characters is Alucard, the son of the count Dracula himself. Also the game series involves many female characters.
All the series is based on a famous novel of Bram Stocker "Dracula". The novel was even included in the official chronology of the series, and the action in the game "Castlevania: Bloodlines" takes place several years after the story described in the novel. One of the characters of the novel, Quincey Morris, who sacrificed himself to kill Dracula, turned out to be descendant of Belmonts. He had a son John and grandson Jonathon, who became the main characters of the games "Castlevania: Bloodlines" and "Castlevania: Portrait Of Ruin" respectively. Various folk monsters are also actively used in the gameseries: zombies, werewolves, mummies, etc. Sometimes one can meet gods from the mythology of different countries, e.g. Adramelech. In Castlevania you can often meet characters from other literary works, for example, Frankenstein's monster, Carmilla and others.
You can play Castlevania flash, swf-file, on this page.