Egon Spengler (Harold Ramis)

Though Ramis passed in 2014, his character is crucial to the DNA of these new films. He, of course, had a daughter named Callie, but he didn’t tell his friends about her. At some point after the original movies, he stole the Ghostbusters’ Ecto-1 and much of their equipment without the other members knowing. That both ended the Ghostbusters and also created a deep resentment between him and his friends Peter, Ray, and Winston.
We learn, however, that he did it to protect them. Egon had discovered that Gozer was prophesied to return and he decided to figure out a way to stop her. He was almost successful, but died while trying to capture one of Gozer’s minions. His spirit remained on his farm and eventually reemerged to help his granddaughter Phoebe defeat Gozer.