Complex sentence: The other protagonist, Samantha Imperial, (Maricar Reyes-Poon) Mateo's and Lia's former ally, and Magnus'vampire daughter was responsible for the Moonchasers with Prof T, gathered valuable intel to sabotage Supremo's agenda.
Split into simpler sentences: The other protagonist was Samantha Imperial, (Maricar Reyes-Poon) Mateo's and Lia's former ally, and Magnus'vampire daughter. She helped Prof T organize the Moonchasers and gathered valuable intel to sabotage Supremo's agenda.