Complex sentence: Further seal impressions show that several deities were worshipped under Peribsen, refuting the monotheism theory, with other contemporary inscriptions indicating that the Egyptian grammar was perfected during Peribsen's reign, which was a time of cultural advancement.
Split into simpler sentences: Further seal impressions show that several deities were worshipped under Peribsen, refuting the monotheism theory. Other contemporary inscriptions indicate that the Egyptian grammar was perfected during Peribsen's reign, which was a time of cultural advancement.