NFE SpDef Defog (Vullaby) @ Eviolite  
Ability: Overcoat  
EVs: 200 HP / 252 SpD / 56 Spe  
Careful Nature  
- Brave Bird  
- Knock Off  
- Roost  
- Defog  
Optional Move(s): 
- Air Slash
- Dark Pulse
- Heat Wave
- Nasty Plot
- U-turn
Optional Item(s): 
- N/A
Optional Ability: 
- Weak Armor
Optional EV/IV(s):  
- 120 HP / 252 SpA / 136 Spe (Modest)
- 192 HP / 8 Atk / 252 SpD / 56 Spe (Adamant)
- 200 HP / 252 Def / 56 Spe (Impish)
Overview: Vullaby acts as a good Defog user and wall in the tier, capable of switching into and threatening out Roselia, the most prominent Spikes setter in the metagame. Its main niche lies in the fact that it can switch into and threaten Roselia better than higher ranked hazard removal such as Servine, Prinplup, Togetic, and Wartortle, and that it has access to Knock Off. It can also check many common Pokemon in the tier such as Servine, Kadabra, Monferno, Metang, Quilladin, and Gabite. It is also immune to Spikes and Toxic Spikes. However, Vullaby is passive, easily chipped, and weak to Stealth Rock.
SpDef Defog: This specially defensive set is capable of walling and checking common special threats in the tier, including Roselia, Servine, Kadabra, special Monferno, and Duosion. Brave Bird hits Fighting- and Grass-types such as Roselia, Servine and Machoke for super effective damage. Knock Off is a very spammable move which removes Eviolite from common switch-ins such as Clefairy, Mareanie, Prinplup, and other physically bulky Pokemon. Defog removes hazards from both sides of the field. Roost gives Vullaby reliable recovery, allowing it to potentially Defog multiple times in a game and continue checking Pokemon.
Checks and Counters: Vullaby is very passive. Physically bulky Pokemon like Clefairy, Mareanie, Staravia, and Togetic can wall it comfortably, recover any chip, and threaten it in return. Bulky Water-types like Marshtomp, Prinplup, and Wartortle also wall and threaten it with Toxic. Steel-types such as Klang, Pawniard, and Lairon also wall physical Vullaby sets and can hit it hard or set up on it. Offensively, Electabuzz and Frogadier can hit it hard with their super effective STAB attacks. Vullaby is also very susceptible to chip damage from hazards and status effects.
Optional EVs/IV(s): An alternative spread of 120 HP / 252 SpA / 136 Spe with a Modest nature is viable for the Nasty Plot, Air Slash, Dark Pulse, and Heat Wave set. This set is somewhat outclassed by Togetic, who boasts better bulk and almost double the Special Attack. However, Nasty Plot Vullaby does have access to an unreliable method of boosting its Speed in Weak Armor, which allows it to act as a cleaner.