Type-enhancing Items

Type-enhancing items are items that improve the efficiency of specific Pokémon types, or defend against them. Some increase certain stats such as Attack, Defense, and others. Items in this category include power boosting items, diamonds, dusts, silks, bands, Plates, crystals, gems, and globes.

Power boosting items
Power boosting items, when held by a Pokémon, increase the power of moves of the specified type by 20% for the whole team.

Diamonds
Diamonds are one-time use items that increase the power of a move that corresponds with the diamond. For example, an Ice Diamond increases the power of Ice-type moves and a Fire Diamond increases the power of Fire-type moves. Besides certain dungeons and Tanren Mines and Tanren Mines Depths, diamonds can be found in the boxes from Togekiss' Egg Swap.

Dusts
Dusts increase stats by 20 for a certain Pokémon type, depending on the dust. Dusts can be obtained by completing missions, being bought from Kecleon Shops in various dungeons, and opening boxes from Tanren Chambers 99 paths of the respective type. Dusts do not have to be held in order to take effect.

Silks
Silks increase stats for a certain Pokémon type by 20, much like dusts. Which stats are increased differs between dusts and silks of the same type. Silks are typically found in sealed chambers, opened with a Silver Key, found within certain dungeons on certain floors. Silks do not have to be held in order to take effect.

Bands
Bands, when held, allow the holder to endure moves of a specific type. For example, the Alloy Band endures against Steel-type moves.

Plates
Plates are held items that reflect damage taken by a specified type of move. However, the holder will still take the damage. Plates are primarily obtained from Tanren Chambers 99 paths of the respective type.

Crystals
Crystals double the movement speed for a certain type, depending on the weather. All Crystals can be bought from Spinda's Cafe for 15 Event Tokens, provided the player's Explorer Rank is at least Bronze, and can only be obtained there. Crystals do not have to be held in order to take effect, but simply kept in the inventory.

Gems
Gems prevent all status problems for a certain type, depending on the weather. All gems can be bought from Spinda's Cafe for 15 Event Tokens, provided the player's Explorer Rank is at least Bronze, and can only be obtained there. Gems do not have to be held in order to take effect, but simply kept in the inventory.

Globes
Globes prevent a certain type from taking damage from a certain move type. All globes can be bought at Spinda's Cafe for 25 Event Tokens, provided the player's Explorer Rank is at least Silver, and can only be obtained there. Globes do not have to be held to take effect, but simply kept in the inventory.

Trivia

 * Shadow Gems used to be obtainable from Tanren Mansion's end boxes.
 * Icy Crystals used to be obtainable from Iceberg Adrift's end boxes.
 * Gems were split into Gems and Crystals on 12th March, 2019. These now exclusively give their corresponding types status immunity and boosted movement speed respectively in suitable weather.
 * Diamonds are main series items normally called gems. They were changed to Diamonds in PMU to not conflict and cause confusion with the gems from Pokémon Mystery Dungeon.