You know Gold d. Roger was the only one to succesfully come back alive when he completed his voyage to the Grand line and put his treasure there at one piece. Then why was it so difficult to get there besides the weather conditions? Why did he succeed where others failed? Did he have a logia fruit type ability? is there even greater weather conditions then the ones we've seen so far? Are there Guardians of the grandline that they have to defeat? Have the marines themselves reached it yet? Though i do not know where the story line is heading, i'm curious to see how this storyline is going to head. The main question really is that why is the grandline so difficult, is it because of the competition, the weather conditions, guardians, or something else?
Anyone got any ideas, how come that place is so dangerous?