Complex sentence: Marisa Coulter kidnaps her daughter, Lyra, relocating her to a remote cave to hide her from the Magisterium, who are determined to kill Lyra before she yields to original sin.
Split into simpler sentences: Marisa Coulter kidnaps her daughter, Lyra, relocating her to a remote cave to hide her from the Magisterium. They are determined to kill Lyra before she yields to original sin.