This interpretation is relatively recent. As per the 1st edition "Dungeon Master's Guide", Vecna only procured this most powerful sword for his chief lieutenant. Similarly, depending on edition and source, its appearance has varied, from a short sword to a wavy bladed two hander. However, it is consistently depicted that the "Sword" is inextricably tied to Vecna's relics. "The reason why Vecna only has a single eye and hand is due to a betrayal by Kas", who used the sword against his former master.