Bravely Default: Start of chapter 6.
I pick up all the blue chests. This gives me lots of chance to fight randoms. Undead die to Phoenix Down spam, most everything else dies to Dark Nebula, which thanks to Magic Sword Amp, Gloom, and Drain spellblade, can fully heal while doing mid-to-high 4 digit damage to everyone. It's not too hard to keep two PCs' Def higher than my DK's attack if she uses a sword (Excalibur, later Chaos Blade) and the other two get Dark Shields, so this works well and blitzes many randoms out of the gate. Black Cait Siths die to blizzard Beast Slayers and Dark Puddings die to Divine Knuckle beatdowns from other PCs. Ambushes and such still suck and can kill me if I get speedhaxed the turn after in particular.
Here are the blue chests of note for me:
-Yoichi Bow: My new strongest weapon, nothing remarkable about it otherwise.
-Muramasa: By far the most important reward, it allows me to Defang (Atk -20%) opponents, which is crucial for various upcoming bosses.
-Chaos Blade: A stronger sword, mostly useful for powering one-handed Dark Nebulas.
-Lustrous Shield: It's a shield with the best Def yet, it nulls light.
-Genji Helm, Royal Crown. Genji Armour: Boring upgrades to defence.
-Luminous Robe: Somewhat more significant, this has the same defences as an Adamant Vest (best storebought light armour) but also boosts light damage by 50%. This stacks beautifully with Divine Knuckles on a Monk.
-Brave Suit: Great defences, and gives you +1 BP to start the battle, which is great.
I get all the rest, mostly selling the superflouous stuff, though I keep the Genji Gloves (highest-def accessory, lol who uses accessories for that this late) and Death Axe (itemcast Kill, which slays enemies 10+ levels below the caster) just in case.
Chaugmar 3 - Well I have to do his dungeon anyway for the Genji Helm, and uh he's really easy now, see Chaugmar 2 except now I have two PCs with Minus Strike and can Defang him to make Energy Burst wussier.
The Dragons
At this point, there are quite a few things in Vampire Castle I want, and with Defang, I finally have the tools to go dragon hunting. So let's talk about them!
The dragons are almost identical bosses. Every third turn they will make the entire party weak to their element, and on all other turns they use a breath of that element. or a singletarget physical which isn't too scary. The big problem is that weakness + dragonbreath can OHKO people if they aren't defaulting, though tankier PC, and I'll be seeing that a lot. Defang reduces this to the point where tankier PCs can avoid this, which more importantly means they can avoid a 2HKO if they default. Since they can only use breath two turns in a row (since every third is used to inflict weakness), this is really key for having anyone but counter-users survive.
Nothing Ventured with Drain Spellblade is key to the fight, and I have two people (the maximum possible at this point) with it, allowing me to do good damage with draining counters on the turns breath is used. The other two PCs just try to survive on the breath turns by defaulting, then heal up. The Dark Knight will use a draining Minus Strike and Muramasa's Defang on the third turns to keep his Atk under control, while the Monk uses Pressure Point which does plenty of damage against their defence, so they basically use these turns to heal up. Counter-users can either default to save BP on the third turns, or refresh spellblade.
That's the theory anyway. If things go wrong then I try to use extra turns to revive, use X-Potions, etc. Generally any problems are manageable. Onto the specifics...
Salamander - Fire dragon. Unremarkable. Iceflame Shields null the first two turns, getting me plenty of time to set up. I know he's the easiest so I fight him first and use him to get my strategy down.
Wyvern - Wind dragon, also unremarkable, except this time the first two turns aren't free. One of my counterers has the Brave Suit, so I have her use Drain / Defang / Nothing Ventured on turn 2 to hopefully weaken the second breath if needed, and more X-Potions are required to patch things up in these opening rounds. But once I settle in, easy.
Shinryu - Light dragon, breath inflicts blind. Monk's blind immunity goes on all PCs, at the expense of some HP, typcially. Lustrous Shield can protect one PC who uses Defang turn 1. Resists holy, weak to dark, which means my Monk's Pressure Point is far weaker, but Dark Nebula scores a weakness, so I use Dark Nebulas on turn 3 and use Diamond Staff + Dark Shield Pressure Points for healing which isn't full, but tends to be adequate.
Ladon - Earth dragon, breath inflicts paralysis. Ranger's paralyse immunity goes on all PCs. Like wind, there's no easy opening rounds here, but past that there's nothing too notable.
Jabberwocky - Dark dragon, breath inflicts dread. This isn't a problem at all to the counter-users, for whom defaulting is a luxury which I can do without (I just refresh drain spellblade if they're suffering from fear on a turn divisible by three). For the other two PCs, dread could fuck them up by preventing default, so I buy one Courage Ring to go with the one I have already, and give them those. They lose some speed/damage but it's fine. Dark Shields protect both counter-users on the opening rounds.
Mizuchi (7 resets) - Okay this one is by far the worst.
This is the ice dragon, and Its breath inflicts stop ~50% of the time. There's no way to stop that (not even a Ribbon) except with a Time Mage passive, and I have no way to avoid the attack. This is pretty terrible and makes the whole fight a crapshoot. The biggest adaptations I make are to dispense with countering, since a counterstance which ends in my being stopped is a waste of BP. I just try to go for draining attacks on every third turn, applying Defang when I can, and in desperation, trying to go for draining attacks at the start of turns he might attack, if it will take me from "OHKOed even through default" to "can probably survive an attack if not defaulting". It's dicy, and needs some gambles, even on the winning run there are a couple of times where I make plans based on the assumption that if the boss uses Ice Breath this turn, I'll just lose. There's nothing remotely reliable about this strategy, but after a few tries it works out.