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(Some minutes earlier)
As Maria saw Kuro and Raven fighting off against Beowulf, she defended against the explosive attacks of Agatha. The Vampire Lord was able to set her own blood on fire and detonate it, unleashing powerful magical explosions.
However, she merely used them as distraction similar to smoke bombs, as Maria had such an insane amount of Magic Stat and Resistance Skills that she was able to fend off magical damage with ease, even with her low quantity of HP, her defense against magical attacks made her a true tank. Abusing such an overwhelming advantage in the stat department, Maria continued to chase down Agatha, as the Vampire, fully knowing that Maria was probably planning something, continued to fight against her at long distance, attempting to tire out her Mana.
Check "The Protagnist's Sister Is Actually the Strongest"!