Just thought I would share with y'all a fun and easy strat for defeating Narcissa and her wicked field effect!
Arbok and items. Hear me out, hear me out...
Arbok, with shed skin, ev trained, holding a magical seed, with the moveset
Rock Tomb
Acid Spray
Payback
Stockpile
As for items I recommend 30-40 berry ice creams, 20-30 soda pops/super potions, 10 burn heals, a few each of the other status items as well as a few ethers (primarily for acid spray).
You have all you need to out stall her team of stalling. I wiped her team out without ever switching to another mon.