This magic sword of solidified gloom, created when you upcast the Shadow Blade spell at 3rd or 4th level, lasts until that spell ends. It counts as a simple melee weapon with which you are proficient. It deals 3d8 psychic damage on a hit and has the finesse, light, and thrown properties (range 20/60). In addition, when you use the sword to attack a target that is in dim light or darkness, you make the attack roll with advantage.

If you drop the weapon or throw it, it dissipates at the end of the turn. Thereafter, while the spell persists, you can use a bonus action to cause the sword to reappear in your hand.

(Please note that the modifier to add the thrown property gives the weapon an incorrect range ((5/5) instead of (20/60)), and that the modifier to grant you proficiency with the Shadow Blade incorrectly gives proficiency with longswords in general, not just this weapon.)

Tip: Once you add it to your Equipment, you can Customize the weapon to add this to its Notes: Actual Range (20/60)
That at least puts the actual range somewhere in the details of the weapon in Actions.

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

Notes: Replace Damage Type: Psychic, Damage: Psychic, Ignore Weapon Property: Versatile, Weapon Property: Finesse, Weapon Property: Light, Weapon Property: Thrown, Proficiency: Longsword, Versatile, Sap