Early 1800s AD
After the events of Symphony of the Night, the Belmont clan began to disappear. Although the games are hazy as to the exact details, it is important to note that their disappearance created an unbalance in the battle of Good and Evil. Other warriors had to appear and pick up the mantle of "Vampire Hunter".
Castlevania: Order of Ecclesia
As the Belmont clan was disappearing, a secret order of vampire hunters came to prominence. Calling themselves the "Order of Ecclesia," they derived their power from glyphs, spells the Order members absorbed into themselves and then cast, like magic.
One member of the order, the female vampire hunter Shanoa, was among the elite of the order. She was to gain possession of the "Dominus" glyph, a powerful spell that would destroy Dracula should he come back again. Albus, Shanoa's best friend in the order, betrays the group, steals the glyph, and costs Shanoa her memories and emotions (making for a very quiet, emotionless husk of a main character). The order leader, Barlowe, awakens Shanoa after the attack, telling her what happened and ordering the bewildered girl to go out, hunt down Albus, retrieve the glyph and stop him from using it to resurrect Dracula.
During her mission, Shanoa arrived in the village of Wygol where she found that the villagers had all been kidnapped by Albus (Albus was using them for experiments). Shanoa had to venture across the countryside, rescuing the various townsfolk while battling the forces of evil. Once she saved them all, she learned the full truth about the whole quest and what she was really doing for Barlowe:
It seemed that Albus was trying to protect Shanoa from Barlowe. The Dominus glyph was actually an extension of Dracula's own magic, and if Shanoa had used it, the magic would have consumed her. Had she died in casting the spell, her death would have aided further in the resurrection of Dracula. It was further revealed that Albus was experimenting with the villagers because they were the last of the Belmont line and their blood may have made controlling Dominus possible.
Sadly she learned all this after killing Albus and taking the last part of the Dominus glyph from his spirit. More informed and better equipped for the final confrontation against Barlowe, Shanoa took him on and defeated him handily. Barlowe confessed that all Shanoa had learned was true, but his death would assure Dracula's resurrection anyway. Shanoa was forced to go to the newly re-awoken Creature of Chaos and defeat the beast within.
Battling past all the various foes and beasts in the castle, Shanoa reached the final room and confronted the Dark Lord reborn. She cast Dominus, sealing the demon king again. Albus's spirit returned, giving up his existence to protect Shanoa, saving her life.
Shanoa escaped as the castle crumbled. All records of the order disappeared after these events (so, you know, forget you read this).
The exact date of this adventure is not currently known. Officially it happens sometime in the "Early 1800s", but before the events of Circle of the Moon (if that game is still even in continuity -- a matter of contention itself). Presumably it couldn't have happened too long before 1810, as Richter was still alive and active in 1797 (the time period for Symphony of the Night). 1810 seems like the safest minimum date it could have happened.
Shanoa appears in the game Castlevania Judgment as an unlockable character. There she is as she was for most of Ecclesia, emotionless and with no memory, having been pulled out part way through Ecclesia. Her story says that she would go back to hunting down Albus after her brief stint in the Judgment tournament.