The items you give your Pokémon to hold have a significant impact in battles against other Trainers. Items carried by your Pokémon can help you deal more damage, withstand more attacks in battle, and even perform complex strategies that you might not be able to do with just moves and Abilities.
These items may appear to provide a minor boost in certain elements, but it is this very fact that gives you an advantage over other Pokémon who do not have an item. Some may be general, whereas others may be specific to a type, Pokémon, or condition.
About Black Sludge and how to get it:
The Black sludge is an item that immensely affects battles while using Poison type Pokémon. The item recovers HP for any poison type that holds it, while lowering HP for others.
It can usually only be found with a 5% chance held by a wild Croagunk, Toxicroak and Grimer. While a wild Muk has a 50% chance of holding the Black Sludge. It is pretty evident due to the appearance and resemblance to Muk’s sludge.
Where to find Croagunk, Muk, Toxicroak and Grimer:
Toxicroak and Croagunk:
They have a good balance of stats, with attack being its strongest. They both have two common innate abilities. If an opponent has a move that is super-effective against it or a One-Hit-KO move, a Pokémon with Anticipation will shudder when entering battle. Dry Skin is an Ability that affects the user’s HP in battle based on the weather, with Rain increasing HP by 12.5% of its maximum HP each turn and Sunlight causing decrease in HP by 12.5% of its maximum HP. It’s final ability may poison opponents when they make contact.
Croagunk can be found in the Pokémon hideaways Bogsunk Cavern, Riverbank Cavern, Still-Water Cavern, Great Marsh and Swampy Cave. While Toxicroak can only be found in Great Marsh or through evolving Croagunk. Croagunk evolves into Toxicroak after reaching level 36.
Grimer and Muk:
They have pretty High HP reserves, while having good attack and special defense stats. It is moderately bulky and a good offence with it’s sludge body that can poison opponents on touch. They are both Poison types that will take more damage from Ground and Psychic type moves and less damage from Fighting, Poison, Bug, Grass, and Fairy type moves as a result of this. They both have a 10% chance to cause the opponent to flinch when hit by damaging moves and their other ability prevents items from being stolen or switched.
Grimer can be found around Route 212, Swampy Cave, Stargleam Cavern, Dazzling cave and Bogsunk Cavern with a 22% spawn rate while Muk can only be obtained through evolution. Grimer evolves into Muk on reaching level 38.