Double Flail (5e Equipment)
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Martial Melee Weapons
The double flail is a flail with two chained heads. It can be used to make a single swung strike, but a master can spin the heads to make two strikes.
When you take the Attack action and attack with the double flail, you can use a bonus action to make another attack with the Double Flail. 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.
If you have the double weapon master feat, you may add your ability modifier to the damage of the bonus attack.