Plachtas 5th memory involves unlocking the recipe for Stahl Metal. This one is far less involved than the previous few memories since all you have to do is synthesize items and use items.
Let’s start off with unlocking some recipes! First, we need to unlock the Neutralizer G. For this recipe you have to buy and sell 300 cole worth of items. This is easy enough, as you can just buy some stuff you need and sell stuff you don’t.
Next, we have the Refuel Bottle, which you can get the recipe for by investigating the pond in the Forgotten Nursery.
To unlock Bottled Misfortune, you have to intentionally part wipe. Go somewhere with a powerful monster, such as the lightning beast from Prospectors Stand. Just keep defending and taking hits until you have a full party wipe. You’ll spawn back at the Atelier with Bottled Misfortune unlocked.
To unlock the Bomb you have to craft an Uni Bag with the “explodes” effect. This is done by getting the middle bar to over 50 while synthesizing one.
For the Monochrome Grass you just need to have Monika use her Brave Heart and Light Edge abilities.
Now we have to do some events if you haven’t done them already. First, go to the cafe and you will get an event for “strange noises” coming from one of the cabins at Pilgrim Road. Go there at night and investigate the cabins until you meet Fritz. A short cutscene will happen and then you can go back to Mr. Horst for another short cutscene.
Next you will need to talk to Leon in the street area, she’s opening up a clothing shop and will ask you to synthesize some Cloth for her. After you have some cloth go back to her and she will give you 1000 cole as a reward, and her shop will be open. You can craft armor and buy materials here. Now back to recipes!
You can unlock the Practice Cauldron once Corneria opens her shop, you really just have to keep going back to the street day after day until you’ve done enough events and cutscenes for her to open shop. At her shop you can set certain ingredients for her to duplicate which you can buy from her. This is especially useful for ingredients that are hard to come by.
To unlock Alchemy Drops synthesize Neutralizer R using Kirchen Milk, and give it the Kirchen Bell Special trait. Then, use that Neutralizer R to synthesize honey and transfer the Kirchen Bell Special trait to the honey.
After this, all that’s left is to synthesize and use items. You get the most experience towards the next memory by using items, so synthesize some bombs, uni bags, or berg medicines and go out and use them during combat. After completing the memory, you will unlock Stahl Metal.