Name: Blessed Bismuth (Tentative title; if something works better, feel free to change it.) P/W/C Type: Not sure, as this is a material; I guess if I had to guess, Courage? Appearance: A bar of Blessed Bismuth appears as a silvery, pink or purple bar. Description of Function: Metallic Material treasure. This is basically meant to be the stuff the Sacred Shield and its derivatives are made of, so it's a bit frailer than other materials, but slowly regenerates, and anyone cursed (read: Dark Affinity) will feel discomfort or fear around it. Limitations: Frailer than other materials, cannot be used with Dark Affinity, and (maybe? Not sure if it warrants this, but can't hurt to list it as possible)cannot be mixed with other metals.
A metallic material that slowly regenerates? There is canon precedence for it, like you said. I like that it's balanced by being frail, as it is in Skyward Sword. I would actually be fine with this being mixable; it gives crafters a little more power, and I don't really see this being OP because of the frailty clause. The DA bit's a nice touch, too. [1/2]
Sorry for the wait, UD. I also beefed the DA thing to include undead creatures- I hope that's already by you, UD. How's this look? `Blessed Bismuth Canon, Magic Tier - Utility [Enchantment], [Magical], [Material] 25 rupees This silvery pink metal was used to craft the legendary Sacred Shield of old, and it can be used in crafting by a player-character with a sufficiently-related level in the Crafting treasure. While frail, this material slowly regenerates, repairing any damage done to it. Additionally, any undead creature or person with Dark Affinity will feel discomfort and fear while around anything made from a bar of Blessed Bismuth.