The Demon Castle War, also known as the Battle of 1999, is a fictional armed conflict between the forces of good and evil that occurred in the year of 1999 and which culminated with the total destruction of the Dark Lord, Count Dracula.
The very first mention of this war appears in Castlevania: Aria of Sorrow. In said game, some enemies Soma Cruz encounters in Dracula's Castle, the Zombie Soldier and the Zombie Officer, are the reanimated corpses of soldiers who died 36 years ago, indicating the date of the war to be 1999, as Aria is set in 2035. It remains unknown who these soldiers fought for during the war, although it's possible they opposed Dracula's forces, or that they even fought on opposing sides, as the Zombie Soldier is portrayed as a zombified common human soldier in military uniform who attacks with an army knife and grenades, while the Zombie Officer is physiologically bulkier, less human-like, and he fights with a large sword (probably of medieval origin), which is a far cry from the usual military armaments of the time the war was held.
The specifics of the war are never directly explained in the game, but it's likely that it involves the events that led Julius Belmont to defeat Dracula once and for all. Whether or not the exact details will ever be known remains a mystery, although it's known that Alucard, Dracula's son, was also directly involved.
Furthermore, as an explanation for the Vampire Killer being entrusted to the Morris Clan, Eric Lecarde mentions that, due to the predicted war in 1999, the Belmonts themselves were inexplicably forbidden to use their family whip for an indeterminate amount of time before (possibly starting from Castlevania: Bloodlines), with the Morrises and others forced to "fill-in" for eventual or premature resurrections of Dracula.
As of now, there's no game in the Castlevania series which depicts or explains the events of the Demon Castle War.
Besides Alucard and Julius Belmont, other characters who could possibly have been involved in that event include Jonathan Morris, Charlotte Aulin, and Stella and Loretta Lecarde, although they would all be in their 70s by then. Saint Germain also hinted about being a visitor to the events leading to Dracula's destruction and could therefore have been involved in the war as well or been a witness to it.
- "Soma, do you know the story of Amanoiwado Shrine?"
- "In the story, Tensho Daijin hides herself in the shrine to calm Susanoo down."
- "Tensho Daijin is the sun. The act of hiding symbolizes an eclipse."
- "By hiding herself away, she was able to contain Susanoo's anger."
- "For that reason, eclipses are thought to confine anger and evil intentions."
- "Yes, people have prayed to eclipses for centuries."
- "And the Hakuba Shrine is a shrine for this very purpose."
- "And usually, we only conduct ceremonies for Japan's eclipses, but..."
- "In 1999, a ritual was conducted in Europe..."
- "Yes... That's what I was told."
- "And that's when Dracula's castle was sealed inside it..."
- During a Q&A session on the topic of endings in a video promoting Bloodstained: Ritual of the Night's Kickstarter campaign, a Twitter user asked Koji Igarashi how the Demon Castle War would have played out and what the story behind it could have been. His response was: "To be brutally honest, I'm no longer in a position to have any control over what happens to that series. If, at some point in the future, a writer picks up the game again to bring it back, I wouldn't want to say anything that could hinder their process of reviving the story. So I'd rather keep quiet for that reason. I'm sure there's a lot you want to know, but I can't actually say anything about it."
- In real life, only the August 11th solar eclipse went over Europe in 1999, which included the country of Romania during the afternoon along its trajectory.