Anything that cannot be equipped to the character is consider an item. Anything that can be equipped should be considered Gear and you should view the wiki page on that instead.
These are crafting items that you can use to modify your gear. These are also the items that you would use to trade on the Trade Market
See dedicated Currency Page
These items are to be used with the Grimoire
Owl Feather - Owls
Bat Wings - Cave Bats
Scorpion Tail - Scorpions (critter)
Large Stinger - Hornets (after Queen Bee)
Soulful Ash - Ash Wraiths
Flaming Eye - Ash Wraiths