I am ashamed to say that i managed to get all of the Celestial Weapons (including Wakkas, which took so bloody long!!!).
About the Dark Aeons. The Break HP Limit is close to useless because they often do close to 99k damage, and the most HP you can get is 30k.
What helped me is being able to use the celestial weapons as they can go over the 9k damage limit. My characters all went around the board once so even Yunas little git weapon does 99k damage (thus you can see how sad i was at levelling them up so much - and how easy the final boss was). But more importantly, my characters had the auto-phoenix technique (which IMO is just cheating.lol), so as long as they werent all wiped out at the same time, they manage to get through any battle...
...That is, until i get to the later aeons (Bahamut and those 3 groovy sisters) where they utterly beat the shit out of all players pretty much straight away...
i wasnt sad enough to get those special spheres that let you overwrite the grid (which is the only way to max out every stat) however.
EDIT: Wakkas overdrive is easily the best as it can do about 9 x 99k if your lucky (although he has been around teh entire board, Wakka does about 50-60k per hit for me, so i guess you need to get those clear sphere thingys to see the true 99k power).
). That reminds me. What were Square thinking when they put dark beahumat in the way of an item needed to get Titan's ultimate weapon?!?! Luckily i collected it before he appears.
