An Error Item is any item whose internal ID number doesn't match a valid item ID number in the game's underlying data file: ObjectInformation.xnb. Error items have no associated item data (price, healing effect, description, etc.) and thus default to purchase/sell prices of 0g and descriptions reading "???". An Error Item will display the image matching the item ID's position in the spritesheet Maps\springobjects.xnb, which might be a non-item image (like a mine stone, sparkle effect, etc).
Error Items can be generated by using the item ID glitch with invalid IDs.
It is not used in any bundles.
It is not used in any quests.