This item appears to be a shortsword hilt. While grasping the hilt, you can use a bonus action to cause a longsword length blade of force and fire to spring into existence, or make the blade disappear. While the blade exists, it emits light equivalent to a torch and has the light property. If you are proficient with shortswords or longswords, you are proficient with Wraithburn.

You gain a +3 bonus to attack and damage rolls made with this magic weapon, which deals force damage instead of slashing damage. It inflicts an extra 1d6 fire damage on a hit, or  2d6 fire damage against ethereal or incorporeal targets.

SPECIAL:  This weapon may be wielded by ethereal or incorporeal creatures which use their Charisma modifier, instead of Strength or Dexterity, for the attack and damage rolls with Wraithburn.

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

Notes: Bonus: Magic, Replace Damage Type: Force, Ignore Weapon Property: Versatile, Weapon Property: Light, Damage: Fire, Damage: Fire, Damage, Combat, Versatile, Sap