Muk @ Black Sludge  
Ability: Sticky Hold  
EVs: 252 HP / 4 Atk / 252 SpD  
Careful Nature  
- Curse  
- Poison Jab  
- Rest  
- Sleep Talk  

Muk @ Fightinium Z  
Ability: Poison Touch  
EVs: 252 HP / 252 Atk / 4 Spe  
Adamant Nature  
- Gunk Shot  
- Focus Punch  
- Shadow Punch  
- Ice Punch  

Additional Moves: Fire Punch, Explosion, Substitute, Thunder Punch
Additional Items: Choice Band, Assault Vest
Notes: Curse Muk is one of the best special walls in the tier and a good set up sweeper. It need teammates who can beat Steel- or Ground-type Pokemon. As such, Magnet Pull Probopass is a fantastic way to trap and beat Steel-types such as Mawile, and Silvally-Water can take care of Golem.
-Fightinium Z with Focus Punch gives Muk the ability to dent common switch-ins such as Probopass, Golem, and Mawile. However, a CHoice Band set can be used with Fire Punch over Focus Punch, giving Muk wallbreaking potential. Choice Band boosted Gunk SHot hits extremely hard, and also gives Muk the ability to revenge kill Psychic-types such as Mr. Mime and Grumpig with SHadow Sneak. 
-Assault Vest can be used to act as a special sponge for offense or balance teams, tanking hits from Rotom-Frost, Combusken, and Chatot. 
-Subtitute+Focus Punch may be used, but Muk does not want to give up coverage options. Explosion and Thunder Punch are also options to hit Torterra, Poliwrath, and Pyukumuku respectively. However, these moves are generally inferior to standard coverage options and used as niche lures.