You have a +3 bonus to attack and damage rolls made with this magic weapon. When this weapon reduces a creature to 0 hit points, the creature doesn't die. Instead, infernal runes appear as if carved into their flesh and they're healed to 1 hit point. They now have the paralyzed condition until the condition is removed by a Lesser Restoration spell or similar magic. When the condition is removed, the runes disappear. At the start of each of their turns while they're paralyzed, the creature suffers immense pain and gains a level of exhaustion.
When you take the Attack action on your turn and attack with a Light weapon, you can make one extra attack as a Bonus Action later on the same turn. That extra attack must be made with a different Light weapon, and you don't add your ability modifier to the extra attack's damage unless that modifier is negative. For example, you can attack with a Shortsword in one hand and a Dagger in the other using the Attack action and a Bonus Action, but you don't add your Strength or Dexterity modifier to the damage roll of the Bonus Action unless that modifier is negative.
When you make the extra attack of the Light property, you can make it as part of the Attack action instead of as a Bonus Action. You can make this extra attack only once per turn.