In the end, the 'greatness' of an ungraded runic armament was tightly restricted.
As they were made out of ordinary materials, the runic armaments Nial created could never exceed a certain threshold.
There were limitations but with the use of runic constellations, it was possible to create a condition where one could nearly reach the material's limitations.
This was what Nial was trying to do by casting a weapon made out of Black iron before engraving the runic constellations he had learned on the warm blade.
It was obvious that the engraving process on shaped hot iron was far more difficult than a piece of paper, however, Nial solved this rather easily.
The first weapon he cast was a broadsword. It had a wide blade which left enough space for Nial to inscribe the runic constellations he had recently learned.
He didn't crave to do anything complicated such as engraving the runic constellation around the edge, altering its size or shape.