Character Creation

Weapon (any sword), uncommon (requires attunement)

You gain a +1 bonus to attack and damage rolls made with this magic weapon.

Curse. This sword is cursed and possessed by a vengeful spirit. Becoming attuned to it extends the curse t oyou. As long as you remain cursed, you are unwilling to part with the sword, keeping it on your person at all times. While attuned to this weapon, you have disadvantage on attack rolls made with weapons other than this one.
In addition, while the sword is on your person, you must succeed on a DC 15 Wisdom saving throw whenever you take damage in combat. On a failed save, you must attack the creature that damaged you until you drop to 0 hit points or it does, or until you can't reach the creature to make a melee attack against it.
You can break the curse in the usual ways. Alternatively, casting banishment on the sword forces the vengeful spirit to leave it. The sword then becomes a +1 weapon with no other properties.