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Board Thread:Series general discussion/@comment-24760042-20160525170802/@comment-5019018-20160525175343
Haven't most antagonists been historical figures? Haytham and Achilles are the only fictional antagonists I can think of, off the top of my head.
To answer your other question, I quite like knowing who I'm aiming for at the start. It gives a sense of purpose and anticipation. It was years ago, but I was very excited to eliminate the Borgia when I started Brotherhood. I don't mind late-story plot twists though.