Gourgeist-Large @ Colbur Berry  
Ability: Frisk  
EVs: 252 HP / 252 Def / 4 Spe  
Impish Nature  
- Synthesis  
- Will-O-Wisp  
- Leech Seed  
- Foul Play / Seed Bomb 

Gourgeist-Large @ Leftovers 
Ability: Frisk
EVs: 252 HP / 88 Def / 104 SpD / 64 Spe
Impish Nature
- Will-O-Wisp
- Synthesis
- Seed Bomb / Leech Seed
- Foul Play / Leech Seed

Additional Moves: Trick Room, Magic Coat, Explosion, Toxic
Additional Items: Yache Berry
Notes:
-First set has maximum physical bulk in order to live two Choice Band boosted Returns from Stoutland. Both 24 and 64 EVs can be added into Speed to creep base max neutral Base 40's and 50's respectively, at the expense of physical bulk.
-Second set is taken from gen 6 Gourgeist-L PU analysis: Lives one Overheat from Zebstrika, outpaces Golem, and the Defense EVs with an Impish nature maximize physical bulk.
-Gourgeist-L can run a Trick Room support set with Explosion and Magic Coat, but faces stiff competition from Dusknoir, the superior Trick Room setter.