Kalibrex’s Penetrating Swing (Cleave)

You've learned how to put the weight of your swings to use when fighting multiple enemies surrounding you. Once per turn, when you have dealt enough damage to a creature to make it drop (typically by dropping it to below 0 hit points or killing it), you get an immediate, extra melee attack against another creature within reach. You cannot move before making this extra attack. This extra attack does not count against extra attacks granted by the Extra Attack feature. The extra attack granted by this ability uses the same proficiency and ability score bonuses as the original attack.