Pelledura (Marvel Scale)

Introduced in Generation III, Marvel Scale boosts the Pokemon's Defense stat by 50% whenever it is affected by a major status condition -- burn, freeze, paralysis, poison, or sleep. This defensive boost does not count as a stat stage modifier, meaning it cannot be Baton Passed, copied by Psych Up, or negated by moves like Haze or Clear Smog.

The most common competitive application pairs Marvel Scale with a Flame Orb. The self-inflicted burn activates the Defense boost reliably on the first turn, and since the boost is multiplicative with the base Defense stat, it stacks with any actual stat stage changes from moves like Coil or Stockpile.

Found on only 3 Pokemon -- Milotic (where it served as a signature ability before Generation V made it available to others), Dratini, and Dragonair -- Marvel Scale transforms Milotic into an exceptionally bulky physical wall that becomes progressively harder to break as status conditions are applied.