The Blade of Binding is a living artifact, granting control over demons.
It was forged by the angel Sarah, who traded Kiril's soul to Kha-Beleth in exchange for free travel through Sheogh. According to Kha-Beleth, she intended for the weapon to "save Ashan from darkness."
The weapon eventually came into the possession of Lasir, allegedly recovered from the deceased Demon general during the Fourth Eclipse.
Lord Bloodcrown's search for this blade prior to a Lunar Eclipse 40 years before Heroes of Might and Magic V saga led to the events of Might & Magic: Clash of Heroes.