This recipe requires an artifact ingredient. Hielo eterno must be present in your inventory or the settlement's storage for the recipe to show up in the crafting station.
You can learn more about this from our Crafting Artifacts, Cooking Recipes and Schematics guide.
THIS IS BOP DONT LISTEN TO GUY BELOW
Must have item 'Eternal Ice' in inventory to see this.
Any idea how this is obtained? I notice none of the 600GS BOP Legendaries (e.g. Musket of Unseen Power) seem to have sources.
You need the ARTIFACT aka Eternal Ice for this to show up to craft at the Arcana Repository. Even though the "Eternal Ice" is NOT BoP, the weapon itself IS indeed BoP. You MUST be Arcana 200 to craft this YOURSELF.