A hero item is an item in which is associated with an iconic character in the game. This may be because they are featured as a key role in one or more quests or that they are simply mentioned in a lore book or elsewhere in the game. Hero items can be obtained as ultra rare drops but only while performing certain activities within the game.
As of March 2018, there are currently 3 hero items available to obtain in the game which can be seen in the below table, alongside their current Grand Exchange prices:
|Hazelmere's signet ring||1,432,268,388|
|Orlando Smith's hat||2,106,582,147|
|Tavia's fishing rod||1,466,249,985|
Each item can be obtained via a different method and usually with different requirements in order to "trigger" the chance of obtaining said item. For further deatils about each item, what it's special effect is and how to obtain it, visit the respective hero items wiki page.