Team Plasma N
Pokemon:
Boldore (Lv. 28) Rock
Joltik (Lv. 28) Bug/Electric
Klink (Lv. 28) Steel
Ferroseed (Lv. 28) Grass/Steel
Type Weaknesses and Resistances:
Boldore is weak to Grass, Water, Fighting, Steel, and Ground.
Joltik is weak to Fire, Flying, Rock, and Ground.
Klink is weak to Fire, Fighting, and Ground. It will be resistant to pretty much every other type, excepting perhaps Electric, and is immune to Poison.
Ferroseed is weak to Fire (4x) and Fighting. It is immune to Poison.
Recommendations:
Krokorok can pretty much manage this at Lv. 29+. Your starter and simian Pokémon (Lv. 30+) can still manage it themselves, though; it is just that Krokorok covers most of the opponents' weaknesses.
After the battle, Prof. Juniper and Bianca appear and speak with N and you.
After the conversation ends and you regain control, you can now leave through the exit nearby to arrive in Mistralton City.