03 - True Ancestor
This is the general term used to describe all species that survive and thrive off the consumption of blood. As for creatures given appellation True Ancestor, they are considered the embodiment of the consciousness of the planet. Despite this, however, every legend regarding these creatures agrees that they not only drink the blood of humans for nourishment, but also out of sadistic pleasure.

Fate/EXTRA - Arcueid Brunestud (Berserker) Matrix