Lot of good ones in here. Only idea I can think of is The Black Company. Not specifically to follow Croakers story either. Could be about battles and drama of the past from the annals.
Goblin and One-Eye would be fucking awesome as the main characters, or Raven. Hell even a story about how the Silver Spike came to be would be a good movie.
No fuck that Croaker is the bad ass mofo and his story should be the first movie. Make it an unknown actor who can be humble but also a bad mofo who everyone is like JFC dude!
If you did a TV series it could be like True Detective. Each season being a different timeframe. The Taken being the few reoccurring characters. But even then a character like Shifter could be portrayed by multiple actors.