The Potion of Harming deals instant damage, reducing the target's health by 6 points (3 hearts). It is brewed by combining a Potion of Poison or Potion of Healing with a Fermented Spider Eye in a Brewing Stand. This potion is highly effective as a weapon in combat, particularly against players and mobs, but it has no effect on undead mobs like Zombies or Skeletons, which are immune to damage from it. Use with caution, as it can also harm the user if improperly handled.