When an opponent uses an attack that requires physical contact against a Pokémon that has the Iron Barbs Ability, that opponent suffers damage equal to one-eighth of its Maximum HP. This effect repeats for attacks that hit multiple times, such as Double Kick or Fury Swipes--the Ability activates for each hit.
For example, if Fury Swipes were to hit a Pokémon that has Iron Barbs four times, the user of Fury Swipes will have lost four-eighths (or one-half) of its HP.
Iron Barbs doesn't have an effect in the Overworld.
Pokémon With Iron Barbs