A sword is an extension of the limb. A weapon that's sole purpose is to reap the lives of the enemy who tries to take something away from you.
A sword is the embodiment of the soul, it was the reflection of one's dao and the truth behind every swing a PR actioner strives to perfect.
A sword must have the ability to encompass the comprehension of its user, never being ahead nor falling back in terms of its ability to draw out every bit of essence in a single sword swing.
These philosophies are the embodiments of the Natal Sword. The sole weapon any Martial Practitioner needs. It was their partner, their limb, and even life.
It could be forged in any way the cultivator willed it to be forged. It could be forged in any material, but the presence of intense heat must be present in order to melt and create the weapon you wish to forge.