He introduced a monotheistic cult around the one true god Aten and changed his name to Akhenaten ( He who pleases Aten.  
The cult he created was based on multiple gods, including Aten.
mnli hypothesis: The cult he created was based on multiple gods, including Aten. premise: He introduced a monotheistic cult around the one true god Aten and changed his name to Akhenaten ( He who pleases Aten.  