Dracula
This is the name used by at LEAST three vampires (or equivalents) over the centuries. It is the most famous and powerful vampire of them all. Any vampire who has used the name is a paragon of his bloodline, including but not limited to the Dark Lord himself, his reincarnation, the Impaler, and a Dead Apostle, each of which is exceptionally powerful in their own right. The name 'Dracula', overall, is just a title many have used, but the most notorious one is Mathias Cronqvist.
Mathias Cronqvist
Mathias was Leon's good friend. In the world of knights who lack education, he was a genius tactician who is even called Cronqvist the Wise. Because Mathias' family had books recording secret arts transmitted orally concerning alchemy, a science that experiments with the arcane, Mathias himself had a detailed knowledge of alchemy. His beloved wife, Elisabetha, died from illness while he was on an expedition. Mathias was grief stricken and bedridden and Leon was forced to continue the campaigns without his friend. When Leon's beloved was kidnapped, Mathias told him that it was the doing of a vampire who had a castle in the east.
In fact, Mathias had deceived Leon and was not likely really bed-ridden. In deep mourning, Mathias devised a plan to take revenge on God for stealing Elisabetha by becoming a vampire and living eternally. He used Leon, Rinaldo, Sara, and even Walter and his monsters, and using the Crimson Stone and a vampire's soul, he was reborn. He then offered Leon to join him and become immortal, because Leon suffered the same loss. Leon refused and vowed instead that his clan would forever hunt him. As time went on, Mathias renamed himself Dracula, taken from the romanian word "dracul" meaning dragon and devil.
Dracula.. the most well known with the name, was also known as the Dark Lord, is Mathias Cronqvist reborn. Over the centuries, he has terrorized Wallachia, coming back from the dead, over and over and over, with only the warriors of the Belmont clan, and, eventually, a few others, able to stand in his way. The power of the Dark Lord made Dracula closer to the antichrist or Satan than to a traditional vampire, but over the centuries he had passed on his curse many, many times. Eventually, in 1999, the Belmont called Julius managed to make a direct blow against the Dark Lord and destroy him, seemingly once and for all, but it cost him his memory and the Vampire Killer whip. Thus ended the Dark Lord's existence.
Soma Cruz
And then came Soma Cruz. The reincarnation of the Dark Lord, the youth with the Power of Dominance, able to absorb the souls and powers of the monsters in Dracula's Castle, sometimes erroneously called CastleVania, who managed to first fight his way through the castle, disposing of another pretender to the title of Dark Lord, and eventually defeating Chaos itself, the source of the Crimson Stone's power. He set off to live happily ever after.
But then a year later, the Castle returned, and this time Soma's fate was not so clear. A deception by a crazy cultist led him to believe Mina Hakuba, his girlfriend, was dead, and the power of the Dark Lord overwhelmed Soma once again. He was defeated by Julius Belmont, Alucard, Dracula's son, and the witch Yoko Belnades. He did not know at the time that Mina was pregnant with his son, but that would eventually come to light, a few years later.
Vladislav III
Alucard was once known as Count Dracula, also known as Vlad III Dracula, the son of Vlad II Dracul. Born in 1431, he later became known Vlad Ţepeş ("Vlad the Impaler") and as Kazıklı Bey ("the Impaling Prince") by the Turks, gaining a fearsome reputation throughout the lands. He is arguably the first vampire that ever existed.
It is revealed in Alucard's flashback in Chapter 70 of Hellsing, that he was enslaved by Ottoman conquerors when he was a child and sodomized by a high ruler. During the whole ordeal, he defiantly clenched a silver cross. When he became the Voivode of Wallachia, he launched an all-out war on the Turks which devastated both sides. Eventually, his troops were defeated, his people were killed (many by his own hands), and his homeland was set ablaze. Vlad himself was to be executed. However, before he was beheaded, he drank of the blood from the battlefield and became a true vampire. When he accepted the powers of darkness, the silver cross he had always carried with him shattered. Centuries later, in 1897, the events of Bram Stoker's Dracula unfold in the back-story of Hellsing. Abraham Van Helsing, Arthur Holmwood, Quincey Morris, and Jack Seward (Jonathan Harker, the last member of their group, is left out of the Hellsing version of the story) were able to defeat Count Dracula and killed those who served him.
He was given a new name, Alucard, by Arthur Hellsing. In 1944, Alucard, along with a 14-year-old Walter C. Dornez, is sent on a mission to Warsaw, Poland, to stop Millennium's vampire production program. They presumably destroyed the project, but it's main architects escaped. Decades later, in 1969, Alucard was imprisoned in a dungeon in Hellsing manor by Arthur. According to Sir Hugh Irons, Arthur Hellsing came to believe that Alucard was "too powerful a drug to be used as more than the occasional medicine".
Alucard
Shortly after Arthur Hellsing's death in 1989, Alucard was awakened and resuscitated by Integra's blood. After wounding Richard, Alucard allows Integra to kill him, thus making her the head of the Hellsing Organization and a master worthy of Alucard's servitude.
