Since the beginning of humanity, several people started dabbling in the arcane arts and becoming witches. When the archangel Lucifer was cast out of heaven by God, he sought to prove that he was right about how flawed and murderous humans are. To do so, he sent out his Demons to convince humans to sell their souls to them and in turn, become Borrower Witches. In many ways, this was proof that Lucifer was right about humans. So, God found a balance, by creating Natural Witches, and with them, Hereditary Magic. While Lucifer needed thousands of Borrower Witches to try to get his point across, God only needed to create a few Natural Witches with godly powers and a desire to do good to prove him wrong.
Since Natural Witches have magic literally written in their DNA, a Natural Witch's blood is magical by itself. One example of this is the witch Qetsiyah, whose calcified blood was used to fuel powerful spells. It can also be used as a recurring element due to its rarity, such as a full moon or a comet. One example of this is Hope Mikaelson, whose blood was used to undo a Desiccation spell while she was still a fetus.
If a Vampire consumes Natural Witch blood, it can produce a variety of effects, depending on how much experience said vampire has in witchcraft. If a vampire with little to no experience consumes Natural Witch blood, the vampire will experience dizziness, aneurysms, and powerful hallucinations. If the vampire has a lot of experience in witchcraft, or even was a witch before turning, they will be able to harness the witch's powers for a short time.