The idea is simple: Having a rare boss drop that goes into your inventory and when used on an item (or via a Blacksmith) it will Reset all Tempering (including Charges). This will further the idea of “an item having a journey”. With an item like this, the journey could be like: “initially I bricked it, but this boss drop gave me a second chance”.
Alternative: If this ends up being too “OP”, then have the item not reset everything, just give you ONE extra Tempering Charge. Same story will apply that you initially bricked it, but you got a second chance, then a third, then whatever… but you had to work for them! Kill those bosses! 1/4 chance to drop? Numbers of course need to be discussed and tested.
It makes sense in the grand scheme of things where if you don’t like your Masterworking you don’t brick your item, but the game basically tells you to do more Pit runs in order to get that second chance, why not something similar with Tempering?
It could be Dropped either as a Material, then have another Square in the Blacksmith’s Tempering Tab with “Reset Item” or as a consumable (like a gem) to add that extra step of clicking on it in your inventory then on the item (like you’re applying this thing to it). This is also important to determine if you want it tradeable or not.
Call it Hellstone, Shard of Jordan or whatever you like. You can even have Inferior and Superior if you also want them dropping in WT3 for players leveling up and state that they only work on Sacred items.
Where do they drop: Word Boss? Maybe… But I think Summoned Bosses make more sense. Or all bosses, but with a sensibly different Chance to Drop, depending on difficulty (Wold Boss<Varshan/Grig<Zir/Beast<Andy/Duri<Tormented versions).
It is indeed something that requires a bit of thinking. Hope the D4 team are reading this or thinking about this already. It kind of bridges this awkward gap that can exist in a player’s mind between trying for a better item to Temper it better vs. going full Masterworking on it thinking that it’s in an ok state. Knowing you can Temper it further if you do some more bosses and this item drops means you get that extra middle step of gameplay (and “item journey”, as they called it).