Complex sentence: As Kirsty looks back at the house, it spontaneously bursts into flame, and Kirsty throws the box into the flames However, a vagrant seen earlier in the film arrives and retrieves the box before transforming into a demonic, winged creature and flying away.
Split into simpler sentences: As Kirsty looks back at the house, it bursts into flame, and Kirsty throws the box into the flames. A vagrant retrieves the box before transforming into a winged creature and flying away.