It is a Magic Weapon +2.
As part of the attack action you can declare a charge draw and force the enemy to pass a Wisdom saving throw against your Spell Save Difficulty Class (if you are not a spellcaster your Spell save DC = 8 + your proficiency bonus + your Mental Abillity modifier, that you choose). If it fails, you roll the attack so if its Armor Class was 10 + Dexterity modifier. Creatures immune to enchantments spells make this roll with advantage.

You can spend 2 charges on a attack hit to deal an additional 3d6 force damage.

Curse: As long as you're set on this katana you regenerate only 1/3 of your hit dice per Long Rest (minimum 1)

Proficiency with a Shortsword allows you to add your proficiency bonus to the attack roll for any attack you make with it.

Notes: Bonus: Magic, Melee Weapon Attack: Slashing, Ignore Weapon Property: Light, Damage: Force, Combat, Cursed, Finesse, Light, Vex