Lanturn @ Leftovers
Ability: Volt Absorb
EVs: 40 HP / 220 Def / 212 SpD / 36 Spe
Calm Nature
IVs: 0 Atk
- Volt Switch
- Scald
- Toxic
- Protect
Lanturn & Roselia form a specially defensive core, with Lanturn checking special attackers that Roselia has problems with such as Aurorus and Raichu-Alola while Roselia absorbs Toxic Spikes and checks grass types such as Lilligant in return. Lanturn also checks Calm Mind Oricorio-Pom-Pom, which I believe to be especially notable as the HP Fighting variant otherwise 6-0s this team.
Lanturn also provides the team with a way to beat Omastar, provided it is lacking Z-Earth Power, which Scarf Scyther is unable to consistently revenge kill.
Lastly, Lanturn can provide a slow Volt Switch for Aggron, giving it an easy way to set up on Pokémon such as Mesprit and Silvally-Dragon without taking too much prior damage.
The EVs in place allow Lanturn to creep Sandslash-A, allowing Lanturn to quickly pivot into Gurdurr. This is particularly useful if Toxic has been scouted prior.
I have opted for the Protect variant of Lanturn as it allows the mon to better stall out Rain and Hail turns in the weather matchup while also stalling out turns to regenerate health and wear down the likes of Eelektross with Toxic.
The team still struggles with hazards, but the team isn't particularly rocks weak outside of Scyther and Froslass/Qwilfish can potentially be scared off by Aggron and Mesprit respectively. That, and there's only so much you can do with one slot.