Simplify the following text for a Grade 3 native English-speaking person.
Original: Eventually , later in Egyptian history that spanned thousands of years and whose pantheon evolved toward a merger of many deities , Serket began to be identified with Isis , sharing imagery and parentage , until finally , Serket became said to be merely an aspect of Isis , whose cult had become very dominant .
Simplified: Later , Serket began to be known as Isis .