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 Held Items, Diamonds, Dusts, Silks, Bands, Plates, Crystals, Gems, and Globes. Many of these must be held in order to take effect in dungeons.

Family Items are also stat-boosters that strengthen certain Pokémon families (evolution paths), such as the Bulbasaur line or the Poliwag line.

Held Items
These 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-use items that increase the power of a move that corresponds with the diamond being held. For example, an Ice Diamond increases the power of Ice-type moves and a Fire Diamond increases the power of Fire-type moves. Diamonds can be encountered in Tanren Chambers, Tanren Mines and Tanren Mines Depths, events such as Holiday Cave, on the floor in Harmonic Tower, and randomly in 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 and being sold by Kecleon Shops in various dungeons or by finding them in events such as Holiday Cave. 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 may differ between dusts and silks of the same type. Silks are typically found in Sealed Chambers, opened with a Silver Key, within certain dungeons on certain floors. Silks do not have to be held in order to take effect.

Possible contents for silk chamber boxes are seen below;

Inferno Volcano, Mysterious Jungle, Voltaic Rainforest, Caustic Sewers, Seafloor Ruins and Dragon's Descent Depths: Respective Silk, Max Revive, Golden Apple, Big Nugget.

All other dungeons: Respective Silk, Revive, Huge Apple, Nugget

Bands
Bands, when held, allow the holder to endure moves of a specific type. For example, the Alloy Band endures against Steel type moves. The known bands are as follows:

Plates
Plates are held items that reflect damage taken by a specified type of move. However, the holder will still take some damage.

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 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 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 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.
 * 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.