Arcueid Brunestud is the princess of the True Ancestors. She is the main heroine of Tsukihime.

Arcueid Brunestud is the White Princess of the True Ancestors. The title of Brunestud was given to those True Ancestors capable of manifesting the Millennium Castle Brunestud, and has been likened to be the vampire royal family, although this is not strictly true. The True Ancestors were a race of beings copied from Type-Moon, the ultimate being of the moon, also known as the Crimson Moon. Long ago the will of the planet had no defense mechanism against humanity, nothing to keep them in check. Thus the Crimson Moon came down and offered to help the planet make a race of ultimate beings to rule over humanity, thus resulting in them being the “consciousness of the planet”. True Ancestors are alike to occurrences such as earthquakes and typhoons rather than individuals as their actions, while evil and without justification, would come as naturally to her (Arcueid and other True Ancestors) as breathing. However the race was fundamentally flawed, they had a desire to drink blood that their original, the Crimson Moon, had. The True Ancestors needed to use a large portion of their power to suppress this impulse, but as there was no cure, and with passage of time the impulse grew, more and more True Ancestors fell and began drinking blood indiscriminately, while others most likely went into eternal sleep.