Meteor Hammer (5e Equipment)
From D&D Wiki
Martial Melee Weapons
The meteor hammer is a set of two bludgeoning weights connected by a chain or rope, typically 6 feet long.
Extended Strike. You can use your bonus action to swing the meteor hammer in a tight circle, preparing it for an extended strike. The next attack you make with the meteor hammer on the same turn is considered to have reach.
Double Weapon. When you take the Attack action and attack with the meteor hammer, you can use a bonus action to make another attack with it. If this attack hits, you deal 1d6 bludgeoning damage. You don't add your ability modifier to the damage of the bonus attack, unless that modifier is negative.
Double Weapon Master. If you have the double weapon master feat, and use a bonus action to attack with the meteor hammer, you add your ability score modifier as normal to the damage roll.