You can use a bonus action to toss this magic sword into the air and speak the command word. When you do so, the sword begins to hover, flies up to 30 feet, and attacks one creature of your choice within 5 feet of it. The sword uses your attack roll and ability score modifier to damage rolls.

While the sword hovers, you can use a bonus action to cause it to fly up to 30 feet to another spot within 30 feet of you. As part of the same bonus action, you can cause the sword to attack one creature within 5 feet of it.

After the hovering sword attacks for the fourth time, it flies up to 30 feet and tries to return to your hand. If you have no hand free, it falls to the ground at your feet. If the sword has no unobstructed path to you, it moves as close to you as it can and then falls to the ground. It also ceases to hover if you grasp it or move more than 30 feet away from it.

You can also use a bonus action to speak this magic sword's command word, causing black flames to erupt from the blade. While the sword is ablaze, it deals an extra 1d6 fire damage and 1d6 necrotic damage to any target it hits. The flames last until you use a bonus action to speak the command word again or until you drop or sheathe the sword.

Deadly sin- When a creature that is good comes in contact with the sword. They have to succeed on a DC 13 wisdom saving throw. If  they fail the save they’re compelled by the blade to act any evil deed the wielder commands. If they save they’re unaffected.

Unbalanced-The wielder of the sword takes an extra 1d8 necrotic damage each time they do an action that would be considered good(decided by dm). This affect can be neutralized if the the bearer can balance(awaken)both yin and yang blade. 

 

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

Notes: Melee Weapon Attack: Radiant, Damage, Combat, Versatile, Sap