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As Erdrich was being healed by the demon blood potions that Blake had prepared, in the side, he put his hand in the floor, and then placed his fingers underground. The bodies of all the soldiers, priests, but mostly demons lying over the floor suddenly began to grow pale and then drier over a few seconds since he did this.
"Blood Extraction."
FLUOOOSSSH!
Below everyone's noses and only with Erika who had a higher perception ability noticing, Blake absorbed the blood of over a hundred corpses surrounding him all while transforming them all into Blood Ki in an instant! Thanks to his improved abilities which he had been enhancing over the years, not only he was able to turn Blood into Blood Ki, but through the "Ki Cleansing Technique" he was able to clean the Blood Ki and then imbue other elements into it to transform its elemental power.
Check "The Protagnist's Sister Is Actually the Strongest"!