A type-enhancing item, when held, enhances the power of attacks with the corresponding type. From Generation IV onward, these items boost the power of moves of the corresponding type by 20%; prior to Generation IV, they give boosts of 10%, except the Generation II-exclusive Polkadot Bow which gives a boost of 12.5%.
The first type-enhancing item to be introduced was Charcoal in A Farfetch'd Tale. Though the significance of Charcoal was explained in detail, and Ash and his friends were given some Charcoal as a gift, its Fire-enhancing properties were not revealed.
A Dragon Fang appeared in Beauty is Skin Deep as the treasure of Clair's family, kept in Blackthorn Gym. It is the fang of an ancient dragon Pokémon that terrorised Blackthorn City. The Dragon Fang is part of a ritual with the purpose of bringing peace to all Dragon-type Pokémon. The ritual involves the Blackthorn Gym Leader placing it on a special ceremonial table, then pouring water over it, causing a light dragon to burst out of it and rise into the sky. Legend says that this light dragon becomes a star and watches over all Dragon-type Pokémon. Another Dragon Fang appeared in Showdown At Linoone as one of the items Tokinpicked up.
A Black Belt and a Twisted Spoon appeared in Climbing the Tower of Success! as items looked for during a scavenger hunt. A Never-Melt Ice was also looked for, but the boy looking for it only found regular ice.
In The Last Battle IV, during the final battle against the Masked Man, Misty, Blaine, and Lt. Surge used Mystic Water, Charcoal, and Magnet to power up the moves of Suicune, Entei, and Raikou, respectively. Notably, the Magnet that appeared was a lodestone rather than a horseshoe magnet as seen in the games, due to the fact that this round was released before the Magnet was given a sprite in the games.
In Generation II, there was one item that would power up each type, with the exception of the Normal type, which had both the Pink Bow and Polkadot Bow. In Generation IV, this is reversed, where each type powered up by one of the items as well as by a Plate, except the Normal type.
However, some types have even more than this, due to incenses.
In Generation V, Gems were added as well, this time including a Normal variety with the other types. Gems, unlike other type-enhancing items, increase damage by 30% (50% in Generation V), but are consumed after use.
Charcoal is the only item available for purchase in a regular store. Some other type-enhancing items can also be purchased, but only from Game Corners.
There is currently no type-enhancing item that enhances the power of Fairy-type attacks.