Little problem here...

[Firo Volondé]

From GameFAQs.

To de-fog and charge your newly acquired magic mirror, talk to the mother and
son at the entrance of Macalania Woods. Find the father at the campsite,
speak to him, and he'll run off to be reunited with his family. Go back to the
entrance and speak with the mother and father again, and keep talking to them
until they mention their missing son. This may take 3 or 4 tries. After they
mention their son, head up the sparkly path to their left into the trees. Bear
north at the first fork, where the son should allow you passage if you talked
to his parents enough times. Show the Cloudy Mirror to the large ambrosia
salad-looking plant, who'll turn it into the Celestial Mirror. If there's a
woman blocking the path instead of the son, either a) you're not far enough
in the game yet, or b) you didn't talk to the parents enough times. With the
Celestial Mirror, you can now open chests and detonate the mandalas
protecting your ultimate weapons.

[10-Breaker]

About the Ribbon. It protects you from every else status, but not death. You need to build up your defensive stats so it has less chance of working. Since you are going after Celestials I tell you that Kimahri's is the hardest and Lu's takes a long time.

[Big D]

Yojimbo uses Zanmato much more willingly if you fill his Overdrive gauge before the fight. Grand Summon is the easiest way to get him into the battle like that; sometimes he'll use Zanmato automatically without being paid, and sometimes it'll only take a few thousand Gil.
So, my simple solution to Dark Aeon problems: Fill Yuna's Overdrive gauge, make sure someone in the battle has a First Strike weapon (preferably Yuna, but it's not essential), and on your first turn have Yuna Grand Summon Yojimbo. If Yuna doesn't personally have First Strike, simply have her trade places with the one who does.

[Jessweeee♪]

I cheated once to get lots and lots a gil and when I paid Yojimbo a ton he used a really wimpy attack

[Hambone]

Use him more. The more you use him, the cheaper Zanmato gets.

[Big D]

Use him more. The more you use him, the cheaper Zanmato gets.

It's small wonder the writers at Videogame Recaps prefer to call him "Hojimbo"...