A quick run-down of the key locations where lost knowledge lies, while the maps vary a lot per seed, the landmark coordinates should stay about the same regardless. All items are under their own separate spoiler so you can safely pick what to check.

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Allows you to mint currency, coins will continue to be relevant on next eras.
Gold = 100$, Silver = 20$, Cooper = 8$.

Additional info:
Less useful than it looks at first glance due a curious quirk:
The three currency ingots aren't affected by the "barter factor", so while a bronze ingot (worth 15$) selling price ranges from 4$ to 8$ depending on location, a cooper ingot will always sell by its original 8$, the same value you get by minting it into coins.
Still good for inventory space and convenience though.

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Defeat the Lv.11 optional boss Piezo.

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Main catch is that the fog's still there, so (afaik) there's no way to have a rest before the battle. Which means that you'll have to fight him on the same HP/EP, fog meter and potion counter you arrived, also no fast travel. Hope you're fond of Souls-like hiking.

Piezo has a spongy health pool of 29k7hp (about 6 Frostbites), and two sentries with 5kp each, paired with simple but heavy hitting attacks, so caution and consistency is the name of the game.
Trim the add count often, wisps/phaseworms will reduce your fog meter so it can last the entire battle, and you do not want a fluffin' Megrin on the way when that Crystal Cannonball charge up sound rings

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One shine ingot each, it is possible to acquire shine ingots without crafting them

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Located south of the ocean you traverse to reach the capital

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