Complex sentence: Crux, the man responsible for the deaths of Elisa's parents unleashes the shapeshifting Miamsa on Elisa, creating a panic in the underworld and seriously injuring Peter, who Elisa had begun caring about.
Split into simpler sentences: Crux, the man responsible for the deaths of Elisa's parents, unleashes the shapeshifting Miamsa on Elisa. This creates a panic in the underworld, while on a personal note, Miasma seriously injures Peter, whom Elisa had begun caring about.