Cosh (5e Equipment)
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simple Melee Weapons
A leather pouch filled with lead shot on a short handle. It is used from surprise to knock the target unconscious rather than as a combat weapon
Knockout If you hit a creature with the weapon and you had advantage on the attack roll, you roll a d10 after the damage is dealt. If this roll is is equal to or greater than the target's remaining hit points, the target falls unconscious as though it had been reduced to 0 hit points. The target's actual hit points remain as they were. If the target would make death saving throws, it still makes the throw, but automatically succeeds. The throw is still made in case a 20 is scored. Constructs and undead are immune to the effect of a knockout weapon.
If the attack would deal extra damage from a critical hit, or a class feature that deals extra damage as a result of having advantage on the attack (such as a rogue's sneak attack), the extra damage is added to the knockout die (instead of reducing the target's actual hit points).