What it is
The Sword of Light is a mystical sword that is said to be able to defeat all darkness.
A legend says that the sword was made from the Light that was sealed in a hidden place in the darkest place in the Universe. The person who forged it was Ethanus Primeus.
Who wields it
The person who wields the weapon is its own Forger, Ethanus Primeus. No other person can wield it, if one person does wield it, the sword would check if the person has any impurities. When the sword finds an impurity it would destroy the person wielding it at the moment.