So, I was searching for the locations of level 3 armor chests in Bitterblack, and came across something interesting on the Dragon's Dogma wiki site. Maybe you guys have seen this before, but I think it might help some of you. I know Hydrargyrus has been killing himself trying to get that sword, others might be grinding for something specific too.
From what I understand, the game sets a counter on when you will purify one of the "extremely rare" items. This counter never changes (i.e. you must purify X number to get one) unless you completely empty your supply of unpurified items (you can trade most of them, but the last one must be purified by you).
If you get something you don't like, you can Godsbane yourself and Retry, then switch vocations of you and your pawn to a different category (Yellow strider/ranger to Red fighter/warrior) and get a different armor type, but it will still be the same stat/piece based on the above mentioned counter. For example, you get purified a Shadow Armor (lower tier) chest piece with health regen. If you Godsbane and switch to fighter/warrior, you will only be able to get the lower tiered chest piece with health regen. According to the guide, the only way to get a fresh item is to change your counter.
Again, this is buried somewhere in the DD Wiki site. These steps diverge at a certain point for weapons vs. armor:
Step 1: Start a new pattern; to do this you need to purify your last Weapon or Armor Lv.3. In the case of weapons make sure you do the same with your Weapons Lv.2.
Step 2: Get a Weapon/Armor Lv.3. Note: You can use the Godsbane to go back to the point right before you purified anything. Make sure you save before you purify as you will use this a lot.
After this point the steps will go separate ways.
Steps (Weapons)
Weapon Lv.2s are crucial; when purified at the same time, Weapon Lv.3s will follow the same pattern as the Lv.2. This can be exploited by saving Rift Crystals and identifying Lv.2s.
Step 3: Get a Weapon Lv.2
Step 4: Purify and look at the results of the Weapon Lv.2.If it's NOT the type of Weapon you need, refer to Step 5.If it is the type of Weapon you need, refer to Step 6.
Step 5: Godsbane yourself. Redo Step 2, 3 and 4.
Step 6: Purify both Weapons at the same time. The Weapon Lv.3 will follow the same pattern of the Weapon Lv.2.For example, you're looking for a Sword and the 5th Weapon Lv.2 purified is Sword. This means the 5th Weapon Lv.3 will also be a Sword.
Step 7: Done
Steps (Armor)
Unlike the Weapon Steps, Armor Lv.2s are not needed, instead the only thing that is needed are Armor Lv.3s. The steps below help determine the interval at which higher tiered Armors will appear, however it does not set the pattern. High tiered Armors that show up first do not count, instead the second purified Armor will. The chances of purifying a High tiered Armor is roughly 10%, the below method should help increase the chances to between 11% to 50%.
Step 3: Get an Armor lv.3
Step 4: Purify and look at the results of the Armor Lv.3. If it's a Low tiered Armor (Sin/Grave/Shadow Armor Set), refer to Step 5.If it's a High tiered Armor (Hellfire/Carrion/Oblivion Armor Set), refer to Step 6.
Step 5: Godsbane yourself. Redo Step 2, 3 and 4.
Step 6: Remember the number of Armor Lv.2s purified before an Armor Lv.3 showed up. This sets the interval at which the next High tiered piece of Armor will come.
Step 7: Keep on getting Armor Lv.3s until you get the piece you need or proceed until you got an entire set. Basically you can continue until you get everything you need.
Step 8: Done