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In the meantime, I rested in my room and contemplated more about this world and this body's abilities.
The reason for the strengthening power this pureblood's blood has is that every pureblood has his or her own power differing from each other, and this body's power is regeneration. To be exact, or more complex, cell manipulation, and it goes both ways. The host can either hasten cell regeneration to improve health, or use it to slow processes or accelerate cell death.
This is how powerful the original host really is. But she became blinded by love.
Of course, there are also limitations to her power. For one, she can only use her power to those she has direct contact with, or those that have her blood, either in them or on their skin, within a range of approximately 200 meters.