I'm now on deeds "hunting" trying to purchase every single possible deed in the game (if not blocked by progression, obviously; plotwise, I've just met Lila).
Some shops probably are missing sellable items, as I've not encountered proper merc missions yet. But what shops actually are supposed to sell deeds? Most deeds I've got are from pouch items shops. Can I assume that accessories, chips, cylinders shops are not selling deeds?
2 Answers
Every shop that sells pouch items will sell a deed, eventually, except for specialty shops like the cookie vendor, the sweets vendor in Fonda Myma, and some others that open up due to events and quests.
You are correct that Aux core, cylinder, and accessory shops will not sell them since they are a bit different in that they do not sell any pouch items.
You may have to raise your dev level or do Merc missions to unlock their full set of goods.
There are 2 main ways shops get more items, and one shop that's a bit weird.
The first is to complete mercenary missions. The "Pink" mercenary missions, found at the bottom of the list for each location, reward contracts. These contracts unlock new items for each vendor. These mercenary missions are typically locked behind Development Level, as well as locations you have visited. By the time you reach Chapter 8 you will have all Pink Mercenary missions unlocked, provided all your locations are 5-Star Development Level.
The second are two shops that have items gated to rare blades. The first is Tilly Bakery in Torigoth, who will only sell a certain item after getting the Kasandra Rare Blade to level 3 Affinity and starting the quest "Our Daily Bread" by sleeping in the Torigoth Inn after getting her to level 3 Affinity.
The second is a book sold by the Book store on Argentum, which will only start selling one specific book after starting a quest with another book related rare blade.
The shop that is a bit weird is the Art Store in Theosir. At some point in the story, he will decide to start selling 5 Art pieces rather than 3 you can buy when you first enter Theosir. I'm not sure what causes him to sell these pieces other than story progression.
Every store, except for the specialty pouch item vendors (like the Food stall outside the Fonsa Mya playhouse) and the Core Chip, Aux Core, Accessory, Exchange, Salvaging, and Rare Items stores (the ones in Torigoth and Mor Ardain) will sell deeds eventually.
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