Complex sentence: The Master, now occupying the body of rock star Gabriel Bolivar, has adopted Goodweather's son Zach as his protégé and is grooming the boy to be his next host body.
Split into simpler sentences: The Master, now occupying the body of rock star Gabriel Bolivar, has adopted Goodweather's son Zach as his protégé. He groomed the boy to be his next host body.