Okay, hear me out
Each chapter would take place 100 years or so after the previous one (I'm not sure when it would begin). The only character that remains consistent between seasons is an immortal who isn't necessary a key character but appears in each season. The immortal character would evolve over time as many characters, with their exploits in various historical periods having an impact on him. I've never seen something quite like that, but it appears to be interesting.