Complex sentence: The majority of Ismāʿīlī follow his descendants through his son Wafi Ahmad (Abdullah ibn Mohammad) who founded the Fatimid Empire, including the Nizari and Mustaali.
Split into simpler sentences: The majority of Ismāʿīlī follow his descendants through his son Wafi Ahmad (Abdullah ibn Mohammad). His descedants further founded the Fatimid Empire, also called the Nizari and Mustaali.