Complex sentence: Angered, he overpowers Valkyrie and attempts to turn her into a vampire but Fletcher stops Caelan and Valkyrie throws Caelan into the sea, closing up Caelans throat, killing him.
Split into simpler sentences: Angered, he overpowers Valkyrie and attempts to turn her into a vampire before Fletcher stops him. Valkyrie then throws Caelan into the sea, closing up Caelans throat and killing him.