Inventor is one of Octopath Traveler 2‘s secret jobs, and has a special method to unlock the skills. Instead of using Job Points (JP), you have to bring items from around the world to the guildmaster items to complete inventions, which can unlock more skills.
You start with two skills, mutable slingshot and springy boots, but the other skills require you to present Akar items. Some items are easy to find – and you probably have them on hand – like soulstones and weapons. However, other items are unique and require you to find them, either by stealing them from NPCs or finding them in chests.
Once you’ve done each of the inventions, you’ll get the Divine skill “All Purpose Tools”, which starts the design time for all inventions, so you don’t have to wait for your next turn. You also get some money and the Mechanical Top Hat armor.
You need characters that can steal items and take down NPCs to get some of these. We recommend using Agnea and Throne.
Below we’ll show you where to find the equipment and unique items you’ll need to learn all the Inventing skills.
Locations of critical scope items
Both items required for Critical Scope (Unerring Earring and Critical Earring) can be purchased from gun stores.
Infallible earring comes from New Delsta (where you get Throne) and Critical earring can be bought from Canalbrine (where you get Castti).
Elementary Bomb bottle locations
To build the Elemental Bomb Bottle you need a Fire Soulstone, Ice Soulstone, Thunder Soulstone and a Rainbow Glass Bottle. The soulstones are easy enough to find – you should get a ton from pickpocketing NPCs, slaying monsters and opening chests.
however, the Rainbow glass bottle is a unique item in a specific chest in the Conning Creek dock area, as indicated below:
Image: Julia Lee/Polygoon | Source images: Square Enix
Tin Horn item locations
The Tin Horn requires an Empowering Lychee (which can be found in loads around the world), a Tin Toy, and a Mythical Horn.
The Tin toys is a unique item that requires you to complete chapter three of Partitio’s storyline. Once you’re done with the department store in Wellgrove, enter at night. A merchant inside will have the toy, which you can take from him:

Image: Julia Lee/Polygoon | Source images: Square Enix
The Mythical horn is in a chest in Nameless Village. You must take out a beastling to get to it:

Image: Julia Lee/Polygoon | Source images: Square Enix
Speed up hammer item locations
The required items for the Haastening Hammer are a Soldier’s Bow, a Great Blade, and a Guardian’s Axe. The Soldier’s Bow can be bought from the shop in Clockbank and the Guardian’s Ax can be bought from the weapons shop in Stormhail.
The Great knife is not a unique item, but you can grab one from this soldier at night at the tavern in Stormhail. Agnea can get it from him if she is level 37 or higher.

Image: Julia Lee/Polygoon | Source images: Square Enix
Locations of Arkar’s Coil Items
Arkar’s Coil is the last skill and requires the most items, all of which are unique: Scrap Metal, an Ancient Cog, and Natural Magnetite.
An NPC in the industrial district of Clockbank has the Scrap and you can use any of the party’s respective item-name skills to get it from them:

Image: Julia Lee/Polygoon | Source images: Square Enix
The Old cog is on Roque Island and you have to get it from an NPC at night. If you can’t access Roque Island, you’ll need to do more of Partitito’s story to unlock the boat. The NPC is in the location below, in the house next to the tavern:

Image: Julia Lee/Polygoon | Source images: Square Enix
The Natural magnetite is located in a mine labeled an “Unfinished Tunnel” connected to Southern Crackridge Wilds. You need to take out the NPC in front of you who warns you that he is too dangerous and open a chest:

Image: Julia Lee/Polygoon | Source images: Square Enix