How to obtain:
A diamond-edged sword.
Translation: Diamond Sword
Alloy refers to a mixture of metals; perhaps this blade was made with an optimum combination of the other sword materials, as since this is the most powerful metal sword.
Vajra is a Sanskrit word meaning both thunderbolt and diamond. In Hindu mythology, Vajra is the weapon of Indra, the Vedic god of rain, lightning and the sky and king of Devas. It is a powerful weapon having the combined features of sword, mace, and spear.It is made up of bones of sage Dadhichi, who gave up his life in order to gift it to Indra to fight Vritra.
From: Weapons (Chrono Trigger)