Chain Knives (5e Equipment)
From D&D Wiki
Martial Melee Weapons
Chain blades are often the weapons used by masters of certain military disciplines, they might occasionally play a key part in the final stages of completing ones' monastic training or be the last weapon for an aspiring weapons master to take up the practice of. This weapon is comprised of blades equal in length (somewhere between that of a dagger and a shortsword), each has thick chains attached to and wrapped around the hilt which commonly attaches to gauntlets on the wielders forearms (e.g. welded, wrapped around, etc.). In olden times this weapon was known as chain knives due to the fact that it is essentially a pair of knives attached to chains, however, this name has been more or less discarded only to be replaced by the more general term of chain blades.
When you hit with a chain blade, you may use a bonus action to attack with the other end of the chain blade dealing 1d4 piercing damage. You may use your Dexterity modifier for your attack roll.