I just got to Pulse, only to find myself very much outclassed by all the enemies around. This excellent question has assuaged most of my fears of having missed something important.
I accepted the first Cie'th Stone mission, thinking that that was the only thing for me to do. I've made it to the cave, and gotten to the first save point. But before the save point, there was an alternate route that led to a boss called Juggernaut.
Unlike the rest of the enemies in the cave, I had absolutely no hope of defeating it. It has over a million HP and I can hardly get an attack in without being annihilated.
Am I expected to be able to beat this thing at this point in my playthrough? I'm trying not to look at walkthroughs, but I peeked at one and it did not even mention the difficulty of this battle at this point in the game. Is this an optional megaboss? I'm not sure whether I can take these missions again after I clear them once; can I come back for it and the Treasure Sphere later?
Or was there something for me to do by following the arrow before I accepted that mission? Should I go back and try to forfeit the mission for now?