Before the ultimate boss fight with the Flesh Incarnate, players must brew a Cure for the Moria Sisters inside the Mansion. To do this, you need to complete a set of tasks, like brewing potions, finding items & whole lot of mini-games. If you are confused about how to finish this, here's a complete guide to help you reach the final part of the DTI Halloween Tales of the Dark King Quest.
How to collect the Moria Sisters in DTI Tales of the Dark King

After the cutscene with Agamemnon, you can walk into a dark, dungeon-like room with lots of cauldrons, stations & other items. Walk up to the table next to the cauldrons in the center to collect both of the Moria Sisters Dolls.
How to find a Cure for the Moria Sisters in DTI Tales of the Dark King
On the same table where you collected the Moria Sisters Dolls, you will find a note with the items you need to make the cure. This list varies slightly for each player but mostly stays the same, with one or two items repeated.

During my run, I was asked to get the following items. Dolls -> Potion -> Spell -> Powder -> Powder -> Scissors -> Thread.
Below, I have listed how to get or make each item, regardless of quantity.
Dolls
You would have already collected the Moria Doll from the table even before reading the note.
Potion

Right opposite the table where you found the note, you can locate the Potion crafting table. You will now be provided with a Solid & Liquid Base. Remember the color of the Solid Base. Play the mini-game to shake up your liquid base, then pour it into the Mortar. On the next screen, select the Solid Base you remembered. Stir the Cauldron until you get your first Potion. Add the Potion to one of the several Braziers next to the main Cauldron.
Spell

Adjacent to the Potion Crafting Table, you can find the Spell Making Table. Here, a spell pattern appears on the screen. Repeat the same pattern by pressing the correct buttons on either side of the screen to copy it onto the paper. Press Submit to make it ready. Also add the Spell to a Brazier.
Powder
Right next to the initial table is the Powder Mixing Table. Check the mini-note for the exact ingredients you need to make the next powder. Now, go through each item and pick the ingredients in the order shown. After selecting everything, add the items to the Mortar one by one. Then use the stone to smash all the ingredients and complete the mini-game. Transfer the powder to the bottle, then add it to the Brazier.
Scissors

Climb the staircase at the room entrance to reach the first floor. Here, check the table in the right-side corridor to find a Pair of Scissors.
Thread

Right opposite, in the other corridor (left), you can find the Thread on top of the table.
Once you add all the items to the Brazier, the central Cauldron will start rumbling, and the Flesh Incarnate will emerge from it. Escape the entity by running straight out of the building where your final boss battle will take place.
For more on DTI, check out Dress To Impress Tales of the Dark King Quest Walkthrough or Dress to Impress (DTI) Private Server Links