Phantasmal Flame is a material which can be used by a blacksmith. It appears as a burning, transparent purple flame belonging to a vengeful poe whose regrets tie him to the material world. A weapon soaked in the Phantasmal Flame by a skilled blacksmith gains the ability to become ethereal. When ethereal, the enchanted weapon has the ability to phase through all non-living objects as if they had never existed; however, it is incapable of phasing through organic beings. When swapping to ethereal mode- and vice versa- the weapon experiences a minor delay of a few seconds before changing to the opposite form. The Phantasmal Flame treasure is an original creation by one of Hyrule Castle's members. Its concept is credited to Eevachu and Clooby.
Click here to see it. Note, I made two additions: 1. I incorporated the armor effect we discussed previously. 2. Since it isn't specifically metal, I enabled it to be used by woodworkers and tailors as well. Let me know if it should be tweaked, or anything.