which mythologies are used in the game?
Greek mythology and Norse mythology
God of War (franchise)
This sets off a series of events that leads to wars with the mythological pantheons. The Greek mythology era of the series sees Kratos follow a path of vengeance due to the machinations of the Olympian gods, while the Norse mythology era, which introduces his son Atreus as a secondary protagonist, shows an older Kratos on a path of redemption, which inadvertently brings the two into conflict with the Norse gods.

who is the first god in god of war Ares, who was killed by Kratos to become the new God of War
wiki:22492174
God of War (franchise) [SEP] Introduction
The Norse era began with the 2018 installment that was also titled "God of War"; it was released for the PlayStation 4 (PS4). It was accompanied by a short prequel, "" (2018), a text-based game through Facebook Messenger. A currently untitled sequel is in development for a 2021 release on the PlayStation 5. Games in the series have been praised as some of the best action games of all time. The series has received numerous awards, including several Game of the Year recognitions for the 2005 and 2018 installments. Some games have also been remastered for newer PlayStation platforms. As of May 2019, the franchise has sold over 40 million games worldwide.