Oathbow
Ranged weapon (martial, longbow), very rare (requires attunement)

When you nock an arrow on this bow, it whispers in Elvish, "Swift defeat to my enemies." When you use this weapon to make a ranged attack, you can, as a command phrase, say, "Swift death to you who have wronged me." The target of your attack becomes your sworn enemy until it dies or until dawn seven days later. You can have only one such sworn enemy at a time. When your sworn enemy dies, you can choose a new one after the next dawn.

When you make a ranged attack roll with this weapon against your sworn enemy, you have advantage on the roll. In addition, your target gains no benefit from cover, other than total cover, and you suffer no disadvantage due to long range. If the attack hits, your sworn enemy takes an extra 3d6 piercing damage.

While your sworn enemy lives, you have disadvantage on attack rolls with all other weapons.

Ammunition. You can use a weapon that has the Ammunition property to make a Ranged Attack only if you have Ammunition to fire from the weapon. Each time you Attack with the weapon, you expend one piece of Ammunition. Drawing the Ammunition from a quiver, case, or other container is part of the Attack. At the end of the battle, you can recover half your expended Ammunition by taking a minute to Search the Battlefield.

If you use a weapon that has the Ammunition property to make a melee Attack, you treat the weapon as an Improvised Weapon. A sling must be loaded to deal any damage when used in this way.

Heavy. Small creatures have disadvantage on attack rolls with heavy weapons. A heavy weapon's size and bulk make it too large for a Small creature to use effectively.

Range. A weapon that can be used to make a ranged attack has a range in parentheses after the ammunition or thrown property. The range lists two numbers. The first is the weapon’s normal range in feet, and the second indicates the weapon’s long range. When attacking a target beyond normal range, you have disadvantage on the attack roll. You can’t attack a target beyond the weapon’s long range.

Two-Handed. This weapon requires two hands when you attack with it.

Damage: 1d8
Damage Type: Piercing
Properties: Ammunition, Heavy, Range, Two-Handed
Range: 150/600
Weight: 2