And to answer your question, Griffith’s dream wasn’t quite that sinister. Being tortured for an entire year after being abandoned by his best friend kinda pushed him over the edge. He was always ruthless, but loyal to his friends. When that loyalty was gone, all he had left was his thirst for power. His whole life had been manipulated by the God Hand to turn him into their fifth member.
The manga explains much more about it. The anime only covers a fraction of the storyline. We probably won’t see more Berserk anime because the rest is too violent to be broadcast on television. There’s been talk of a new OVA series, but nothing’s come of it.