Beads of Ruin decreases the Special Defense stat of all Pokémon on the field other than the Pokémon with this Ability by 25%. The effect does not stack if more than one Pokémon with Beads of Ruin is on the field. If Wonder Room is in effect, the Defense stat is decreased instead. The Pokémon is also immune to other Pokémon's Beads of Ruin.