Note that if you have this sword without the complete outfit, it's suicide to use it. The sword drains the enemies health for each successful strike and heals Geralt, but if you don't have the whole Oathbreaker's outfit, it'll drain Geralt's health over time, making the fights even more difficult since your life will be droping even without being hit.
So, I advise you to craft the two swords after all of the other pieces of the Oathbreaker's Outfit.