Undead who, while maintaining the personality from their previous life, become active as vampire apprentices. A half-baked vampire that in exchange to obtaining physical abilities far exceeding those of humans feel an extreme coldness and thirst. Lower-class knights so to speak.
When those of the VI rank or above carefully suck the blood of their prey, the victims start as a vampire of this rank. They become anemic when bathed in sunlight, but they will not burn at this level.
In magecraft circles, vampires are still considered to be “human” up to this rank. Vampires who have reached the IVth rank can live apart from their progenitor. From the point of view of the progenitor, it is as if the victim has changed from an object to a living creature. Only one person out of a thousand reaches the fourth rank.