Muk

Thickly covered with a filthy, vile sludge. It is so toxic, even its footprints contain poison.

Pokemon Power — Toxic Gas: Ignore all Pokémon Powers other than Toxic Gases. This power stops working while Muk is affected by a Special Condition.

Sludge: Flip a coin. If heads, the Defending Pokémon is now Poisoned.