OOC:
I kept the story a little generic so that there's room to fit into any location that might suffice.
Chuton was an average guardsman in a straightforward job with little complications. His raw strength and golden-scaled dragonborn presence were usually enough to quell any thoughts of resistance. He was dedicated to the job such that he had no familial ties beyond the camaraderie of the force; his parents were long passed and he had no siblings nor romantic interests.
Things changed and his life took on a new direction after a fateful night while on patrol. Chuton and his partner encountered a woman in the process of battering down the front door to a home, armed with a sword and screaming in rage. The dragonborn decided to intervene and used his strength to restrain the warrior with a chokehold, while his partner confiscated the blade. Chuton secured her so that she could not fight back, ignoring her cries to be released and deaf to the claims that she was not the enemy; he reasoned that he was no judge of character and those with greater authority could decide whether or not her claims were true.
That was when the assassin, barricaded within the woman's own home, opened the door and sent a fatal crossbow bolt into her heart. The surprise was enough to allow the assailant to flee, leaving behind the woman's slain family and both guardsmen flat-footed and shocked.
An investigation cleared Chuton and his partner of significant wrong-doing, but their negligence still cost them employment. Chuton was discharged from service and while not prosecuted for the deaths of innocent lives, was exiled from his hometown.
Chuton carried the guilt of that night since, and the experience left a dark pit in his heart. He discovered that he couldn't even find rest without the need to keep his greatsword at his side at all times, as though he needed to be ready to prepare for an attack and leap to someone's defense. He was vaguely aware than whenever he was in a fight, the sight of his own blood would sometimes propel him into a furious rage against the one who drew it, such that he would lose all tactical sense while he focused on the target of his ire.
[ +- ] Sword of Vengeance
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 to you. 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.