Poké-BODY ⇢ Toxic Gas
As long as Muk ex is your Active Pokémon, ignore all Poké-Powers and Poké-Bodies other than Toxic Gas.

{G} → Poison Breath : 10
The Defending Pokémon is now Poisoned.

{G}{G}{C} → Slimy Water : 40+
Does 40 damage plus 10 more damage for each {C} Energy in the Defending Pokémon’s Retreat Cost (after applying effects to the Retreat Cost).