A guide on how to take on the third Totem Pokémon of the game: Totem Salazzle!
Totem Salazzle is a level 22 Poison/Fire-type Pokémon, with access to the following moves:
Torment is a move that makes the target unable to use the same move twice. Toxic badly poisons the target, while Venom Drench lowers a target’s Attack, Special Attack and Speed by one stage if they are poisoned. Flame Burst is a Fire-type move that deals damage.
Totem Salazzle's aura boosts its Special Defense +1. Furthermore, the Totem Pokémon has the Ability Corrosion, which lets it inflict the Poison status condition on Poison- and Steel-types (which normally can't be poisoned). Finally, it hold a Petaya Berry, which gets consumed and raises the Pokémon's Special Attack +1 when its HP is below 25%.
Totem Salazzle can call a level 20 Salandit as ally. This is a Poison/Fire-type Pokémon with the following moves:
Poison Gas is a move that poisons the target, and Venoshock is a Poison-type attack that deals double damage against poisoned targets. Taunt is a move that forces its target to only use attacking moves for a few turns. Scratch is a Normal-type move that deals a little damage.
This Salandit also has the ability Corrosion, making it able to poison Poison- and Steel-types.
Water-types are useful as they resist Flame Burst and can hit for super-effective damage, while also having access to the Z-Move Hydro Vortex thanks to the Waterium Z.
Ground moves can deal double super-effective damage.
Rock can deal super-effective damage and resist Flame Burst, while Psychic just deals super-effective damage.
Super-effective damage is key to this fight (more than resistances) as taking the Totem Pokémon down as quickly as possible is easy enough and important as the Poison status condition can be troublesome if left unchecked for too long.
Wishiwashi is a very good Water-type that is available at Brooklet Hill. If past level 20, the Schooling Ability lets it transform into School Form which has very good offensive and defensive stats. A sufficiently leveled Wishiwashi can OHKO the Totem Pokémon with Hydro Vortex.
If you train enough, a freshly-evolved (level 26) Alolan Dugtrio is also very good; nice Attack and Speed as well 4x effective STAB should deal lots of damage before it gets knocked out (it is weak to Flame Burst).
Mudbray is another viable Ground-type Pokémon that is going to be useful for most of the game.
In practice, almost all Water- and Ground-types are very effective in this battle, so the suggestions above are mostly picked because they are extremely useful in the long run as well as this battle; at this point of the game it is advisable to think ahead.
As with almost all Totem Pokémon battles, it is advisable to focus on the Totem first and the ally later. In this particular battle you should KO the Totem Pokemon as fast as possible.
There is no “hard counter” for this battle, as both Totem Salazzle and Salandit can poison any Pokémon and if this battle lasts long this is going to be a problem. Giving a Pecha Berry to the Pokémon you are going to use the most is advisable, although maximizing the damage with other items is also a good idea. Waterium Z makes things easier.
If you believe you will be unable to KO Totem Salazzle quickly, make sure to have at least two viable moves against it in case it uses Torment.
You may also use the Sleep or Paralysis status condition on Totem Salazzle.