DFOArchive: Black Purgatory Made Simple

For the submission of the Master of the Black Purgatory event, screenshots of explorer club level and character name can be found in this About Me page.
Black Purgatory was released in Korea on Jan 6, 2021 as first part of Winter Festival.
This dungeon is known in the community as Oculus 2.0
You can get reward once per day, twice per week per character.

Table of Contents

Dungeon Set-up & Layout

This dungeon has very similar concept as Operation Hope.
Here it is divided into 3 Crossroads, and each one is guarded with a mini-boss.
Once the mini-boss is defeated, you will be presented with different route options to take to the next Crossroad. The 3 possible options are: Dark Knight, Corrupted Village, and APC Rescue

The illustration below will give you an idea of how the dungeon progress. The route you take will determine the bosses you face and the reward you get at the end.
Here's how the dungeon progresses.

You face Jade (1), then pick your route to the next Crossroad (2).
After fighting the bosses in that route, you face Venta (3), then you pick your route to the next Crossroad (4).
Again after fighting there, you fight Onyx (5). But before her, you get to rescue an APC that give you a random buff and you also get to meet merchant Posha, where you can reset your skill and buy various useful pots.
You then choose your next route (6), fight all the bosses there then meet your final opponent Astaros (7).

So regardless of which route you take, you get to fight at least 3 mini-bosses (one guarding each Crossroad) and you get to rescue at least 1 APC for a random buff.
NOTE: You can retreat without losing dungeon progress. From my understanding, after treating, you start back where you last kill a mini-boss. Keep in mind the more you retreat, the longer you need to wait to go back in. You can use this to your advantages such as resetting skill cooldown before a particular hard boss.

Once the APC is rescued, you can use the buff by using the "Special Dungeon Key" (defaulted as "Tab"). Name of APCs and their buffs below.

While you're in this route, there's a chance a Dark Knight OR a Follower can intrude. Defeat Dark Knight will increase final reward. Defeat Follower will give permanent damage buff. More details below.
Now let's see what you will face if you pick Dark Knight and Corrupted Village routes.

In the image below, each Dark Night (D, Right) is accompanied by a Follower (F, Left), and the pairs are always the same (3 total pairs). You will always fight Follower first, and each successful Dark Knight defeat will grand you more reward at the end. The pairs are:

If you pick this route, you will only fight Follower.
However, there's a chance his Dark Knight can intrude. If this happen, the Dark Knight will have less HP, and defeating this Dark Knight will grant you more rewards as if you were taking the Dark Knight route (yay).
The good thing is each Follow defeat will give you damage boost, 3%, 8%, and 25%, respectively.

Possible Routes

There are endless routes you can take to the final boss depends on your party composition and gears, and you need to weight your risk vs. benefit as well to see how many Dark Knight you want to face.
If you look at the rewards, it's divided into stages. So I will go over the route needed to achieve each stage.

Stage 1

Here you don't take any Dark Knight route at all. So your rewards will be minimal. Take this route if your party is extremely barebone.
In this route you only face 2 Followers and get to rescue 2 APCs.
If your party still really need the damage, you can also pick Corrupted Village route in the beginning (2) to get the 25% boost.

Stage 2

Here you take down 1 Dark Knight.
I know the location of Dark Knight pairs are randomized but I'm not sure they would stay the same if you retreat and take another route.
So even if they are randomized but stay the same once you know which one they are, potentially you choose which one to take out (4 or 6). For example. if you get into (4) and that boss is too hard, you can take Village at (4) and do Knight at (6) instead, and vice versa.
I don't recommend taking Knight at (2) though because you may need that extra APC buff, and since you're only doing 1 Knight, might as well do either (4) or (6).

Stage 3

Here you take down 2 Dark Knight.
There's not really any other way. You can try to take Village at (2) if your party need that extra damage buff.

Stage 4

Here you take down 3 Dark Knight and all 3 followers.
This is definitely the hardest route where you face ALL the bosses and mini-bosses this dungeon has to offer. So proceed with caution.

Boss Mechanics

Tips and Tricks

After defeating Jade, you will have 3 options to pick which route to go next. Paladin Jenna will always spawn in the APC Rescue route.
You can use her 15-sec groggy ability up to 2 times with 60-sec cooldown in between. So unless you're doing the stage 4, always rescue this APC.

If you're out of coin, you can always retreat to town and retry. Retreat will reset all your skills so you can use this as your advantage. However, retreat doesn't reset your 5 coin limit.
However, be careful, the more you reset, the longer you have to wait to go back in (5 seconds, 80 seconds, 100 seconds, 130 seconds, 180 seconds, and so on). So I don't really recommend you retreat more than 2 times.

First, the merchant Posha can reset all your skills for just 1 time (left circle). So you can dump all your skill on the boss before him.
Second, this go in hand with retreating, dump all your skill before the final boss (right circle). After that, you can retreat to reset skills then go back to fight the final boss. Since the first retreat only have 5-sec downtime, most parties use this strategy.

NOTE: This content is focused on sustain damage, so sader should bind 1A to 3A. There you can cast 1A while 3A is on cooldown, and vice versa.
For Stage 1-3, the recommend spots are below. Really self explanatory, here you combine both merchant Posha and town retreat to reset your 1A/3A.