Unleash the entire ATB bar of Blizzard+, the entire bar of Beat Down->Jump to Stagger, the entire bar of Heavy Slashes to deal massive damage. Overclock, and keep Heavy Slashing until eliminated, without even having the chance to stand up. Yay growth!
Speak to the two Yeuls and jump on their platforms to progress as usual.
Take a right in the fork and pick up the Element Lv. 2 in the treasure sphere.
Cast Deshell for the heck of it. Wait a bit before casting Deprotect, but make sure you do it before Megaflare hits.
When the Megaflare has launched you into the air (and dealt massive damage that we have to tank), press the Start Menu and drink a Hero's Potion, which will be queued and used immediately upon landing.
Now use Beat Down-Jump until Stagger, then Overlock right away and start using Heavy Slashes.
As soon as an Overlock ends, Overclock again to not give Caius any breathing time. Keep Heavy Slashing and Overlocking and he will eventually go down.
The key point is that both Bravery and Deprotect needs to be applied simultaneously, and not to let Caius cast any ability after Stagger, which would end your damage chain.
This fight needs to go fast or else we cannot win.
Defense is everything in this fight. Keep Heavy Guarding his attacks (every one of them!) to allow the Angel to keep your health up.
Use Aero+ throughout the battle, to keep the Stagger bar high and to increase your ATB for Heavy Guards.
Use Beat Down/Jump defensively; as your Aero+ will keep Stagger high, a single Jump can often Stagger him easily, even to the 2nd stage.
Do not Overclock, regardless of how Staggered he is. Save EP for any eventual Arise, as you are likely to be left with only 3 EP after Caius. I replayed the battle with different configurations a few times, and managed to beat him without Arise/items, but it is very easy to lose here.
You must block "So Hungry!" as it Dazes you! It comes after "Should I Chomp Them?", and if you do not, the Angel will not be able to keep your health up! He follows "So Hungry!" with one of two powerful attacks, which you must also Heavy Guard, and then immediately after spam Aero+ to regain ATB, as he will start attacking immediately after!
Cautious, defensive play is the only way to defeat this beast.
Continue west to The Residences and speak to Armand, advancing his quest one stage.
Around here is a boy with a flag on his back, speak to him and accept his quest "Faster Than Lightning".
Follow the kid, but do not run so fast that you despawn him, which is very easy. He also needs to reach the destination to complete the quest.
He can either run to the Forsaken Graveyard, for which you need to run to the telephone booth, or the North Station, for which you need to run all the way up to the ticket man. When you hear the Final Fantasy victory jingle, you've won. Speak to the boy and collect your reward.
Run up to the red Cactuar statue and warp to the Sacred Gate.
Run into the hallway to the northeast into the Gallery of Forgetfulness, and set the last tablet.
Pick up the Crux's Base to form the Saint's Crux.
We won't be using it until tomorrow...
Run south and south, and then into the Sacred Grove. Here enemies will spawn.
Stay here and fight Skeletons all day until they are extinct. Keep all Wind-element garb and accessories.
I find enemies are most likely to spawn inside the hallway to the Twilight Gallery, running directly outside of it and along and back the straight path.
Do not use Overclock or EP, we need to regenerate enough to Teleport away (3 EP).
Break all the breakable skeletons in the main room, they will respawn after a while and have a chance of dropping goodies.
If you want, you can switch out Quiet Guardian for Miqo'te and use the new Gagnrad, as it will deal both physical and magical damage with Magic Slash, a special property only available with dual-blades.
Once you see the pink Skeleton, save before striking.
Honestly, Skeleton Ω is very easy to Stagger. Aero+ until the 1st of Stagger, then Jump until 2nd.
At this point, empty out your ATB gauge with Jump, then Overclock once and keep Jumping until out of ATB.
When he recovers he'll use Blood Sword, make sure to Heavy Guard it.
At this point his HP should be fairly low. Keep Aero+ and Jump to Stagger, and he should be unable to do much. Just make sure to Heavy Guard against every Blood Sword attack, as they'll restore their own health in the process.
Defeating it only rewards 2.5 EP, so no more than one Overclock should be used.
Important! Pick up the Bonecracker that is dropped after the battle!
Because we've exterminated all Skeleton before Day 7, we've permanently lost out on the Brittle Bone weapon drops, but seeing as Bonecracker is the stronger version we do not really need to worry about it. You can wait to farm Skeletons until Day 7 if you feel like you've missed out.
Use your EP ability Teleport and go to Ruffian.
Inside the bar area is Jamus, speak to him to complete his quest.
Get on the Angel and ride to Poltae. The path to the south of the Station is the fastest.
Any Reaver on the way should be no problem, use these guys to regain your EP (should be 0 right now). Jumps Stagger easily, especially directly after blocking his first attack when standing. Even though it is resistant to Wind-elemental attacks, I don't see a need to switch. Jumps cannot Launch though, but I'm fond of Heavy Guard at this point, so...
Once you get into the Rocky Crag you'll run into Aster Protoflorians, against which it is probably best to just Overclock once when it is Staggered, and spam Jumps to get it down. Stay away from Magic attacks as much as possible, and guard against its Manadrive Missile and other strong attacks.
Once in Poltae, examine the tiny book lying next to one of the doors of the village (ground level). It is directly north of the general store on the minimap. Here you find Etro's Forbidden Tome.