The Arcane Blade

This artifact was created for the first Knight of Mystra to lead the battle against the initial incursions from Zoreth. The blade and cross guard are made of metals that appear to be platinum and gold, respectively, but both are most assuredly from another plane. The blade has taken many forms over the millenia to suit its wielders' styles, but its sheer power has remained the same. Perhaps other than Mystra herself, no one knows who crafted the Arcane Blade or delivered it to the first Knight.
Only a 20th-level eldritch knight may attempt to attune to this blade. This can occur only after they have gained the approval of Mystra as her next Knight and wielder of the Arcane Blade, typically by completing a grand quest on her behalf. This weapon significantly increases the wielder's offensive capabilities with both sword and spell. However, the wielder cannot stray too far from the sword or suffer severe consequences.
Once a creature attunes to the Arcane Blade, the attunement cannot be broken unless the wielder dies or the sword is destroyed.

Item type

Unique Artifact

Use(s)
Martial Weapon (scimitar, longsword, or greatsword)
Current Wielder
Virgil Halathar