Disclaimer: I don't own Rosario + Vampire
Author's Note: This is my guess at what might have happened in the cannon past. Spoilers for the most recent chapters are present. So perhaps this is an AU.
His ambition started with power.
After siring his race he sought out other races, strong races and took their blood into himself. Eventually his own name was forgotten, replaced with the title he gained, Shinso. Though, like that human concept; there can be only one. After years of gathering powers-blood-, he attempted to take control of the planet.
To wipe out the human race became his ambition, and he certainly came close. His once small lithe body had been mutated by the blood of the multiple ayashi, changing him into a giant grotesque monster. His rage and anger caused him to attack the nearest continent, Asia.
In seven days the continent was aflame.
Then she came, another like him. Vampire born – Shinso – too. He remembered the moment she defeated him, killed him; even in death.
As his large body crashed into the ground, she transformed back into her human disguise, complete with green eyes and long, flowing pink hair. Her two companions stood farther away as she knelt down next to his eye.
She smiled and spoke, but he couldn't hear.
Bloodriver Akasha stared into his eye as he passed into the next world. "You can rest now," she murmured. "Alucard-sama."
AN: Alucard is pictured in Rosario + Vampire II Chapter 13 page 21-22 if you're curious. Akasha is cannon Moka's mother.