Baransuburēdo

This sword is made of many parts, a Blade to cut, a Pommel for leverage, a Grip to manipulate, and a Guard to reinforce.

Blade: 

When you hit a creature with an attack using this magic weapon, the target takes an extra 2d6 Necrotic damage and must succeed on a DC 15 Constitution saving throw or be unable to regain Hit Points for 1 hour. The target repeats the save at the end of each of its turns, ending the effect on itself on a success.

Pommel:

You have a +1 bonus to attack and damage rolls made with this magic weapon now. You can add your Constitution modifier (minimum of +1) to the weapons normal damage. When you attack a creature with this weapon and critical for the attack, you gain hit points equal to the amount of Necrotic damage taken.

Grip:

You have a +2 bonus to attack and damage rolls made with this magic weapon now. The constitution saving throw increases to DC 17. The first time you attack each creature during an encounter with this shortsword, you have advantage on the attack roll. If that attack hits, maximize your weapon damage dice against the target. Additionally, when you miss with an attack using this shortsword, you can use your reaction to turn a miss into a hit. You can do this only 3 times per long rest. 

Guard:

You have a +3 bonus to attack and damage rolls made with this magic weapon now. The constitution saving throw increases to DC 19. When you target a creature with an attack using this weapon, you can invoke the sword’s rune. You then expend and roll one of your unspent hit dice and add the number rolled to the attack roll and take the same number in necrotic damage(this number cannot be reduced by any means). You can choose to invoke the rune after rolling the d20. If this attack hits, you can also roll any number of dice equal to your hit dice and add the total rolled to the weapon’s damage and take the same number in necrotic damage(this number cannot be reduced by any means).

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

Notes: Damage: Necrotic, Damage: Melee Weapon Attacks, Bonus: Magic, disciplined fighter, Finesse, Light, Vex