When it comes to Frank Castle, why he became the killing machine is up for debate. For years, the theory has been that the death of his family turned him into a vigilante. Jason Aaron’s series showed us that it was more than that. The Hand had, well, a hand in creating him.
The Archpriestess followed Frank from a young age and helped mold him into the killer he later became. However, there was someone else. Aaron took a page out of Garth Ennis’ story and added depth to it.
In Ennis’ Punisher MAX: Born, Frank said yes to an entity that would give him a war that wouldn’t end. Readers never knew who exactly it was that was speaking to him. All we knew is that their symbol was a skull. Jason Aaron’s run revealed that it was the Greek God of War that spoke to Frank and anointed him. He’s been his avatar this entire time and kills in his name.
This was also mentioned by Moon Knight during Moon Knight: Midnight Sun, in which Khonshu tells Marc that someone else anointed Frank and he wears their symbol on his chest. The symbol is the same skull that Ares has on his uniforms.