Held Items

Held Items are objects equipped to the monster which increase flat stats and skill power. Some of them increase different types of skill (such as fire or water) while others are for specific monsters. Campaign can drop all Held Items except for Monster specific ones. Those can be obtained through events.

Arceus' Plates
Arceus has a wide variety of plates, which will not only change its type, but also the effects of its skills. Same type pokemon will also receive a buff.
 * Zap Plate (Electro type) - the Ulti has a chance to stun all enemies if the AoE skill has been used
 * Icicle Plate (Ice type) - the Ulti has a chance to freeze all enemies if the AoE skill has been used, weather buff instead of heal
 * Splash Plate (Water type) - ??
 * Insect Plate (Bug type) - ??
 * Pixie Plate (Fairy type) - any fairy skill in the team will trigger a speed boost
 * Fist Plate (Fighting type) - Ultimate - Increase 20% crit and dodge for 3 rounds and fighting damage - single target
 * Stone Plate (Rock type) - the Ulti has a chance to lower all enemies' speed after if the AoE skill has been used, affects opponents' accuracy negatively, weather buff instead of heal
 * Earth Plate (Ground type) - the Ulti has a chance to stun all enemies if the AoE skill has been used
 * Meadow Plate (Grass type) - the Ulti has a chance to poison all enemies if the AoE skill has been used
 * ?? (Ghost type) - ??

Deoxys' Meteorites
Deoxys can take 3 different forms with its meteorites, which will greatly change its skills and buffs.
 * Speed meteorite, increases its speed
 * Attack meteorite, increases its skill power
 * Defense meteorite, increases its defense

Giratina's Griseous Orb
Increases all of Giratina's Skills.

Pikachu's Light Ball
Increases Pikachu type's Skills.

Genesect's Drives
Changes Ultimate attack into the respective type and increases its resistance to this type, increases all of Genesect's Skills.
 * Douse drive (Water type)
 * Shock drive (Electric type)
 * Chill drive (Ice type)
 * Burn drive (Fire type)

Chansey's Lucky Punch
Increase Chansey's Crit by %

Cubone's Thick Club
Increases Cubone's Attack.

Latias' Soul Dew
Increases Latias' and Latios' Sp-Atk and Sp-Def.

Dialga's Adamant Orb
Increases Dialga's Skill Power.

Palkia's Lustrous Orb
Increases Palkia's Skill Power.

Specific Skill Type
It doesn't matter which type your monster is, only the skill type will be buffed, so decide which of your monster's skills is most important.

Metal Coat
Increases Steel, Psycho, Normal skill types.

Dragon Fang
Increases Dragon, Flying, Dark skill types.

Black Belt
Increases Fighting, Poison, Ghost skill types.

Charcoal
Increases Fire, Ground, Rock skill types.

Mystic Water
Increases Water, Ice, Bug skill types.

Magnet
Increases Electric, Grass, Fairy skill types.

Wide Lense
Increases skill accuracy.

Leftovers
Recovers each turn a percentage of monster's max HP.

Wise Glasses
Increases power of Sp-Atk Skills.

Muscle Band
Increases power of P-Atk Skills.

Quick Claw
Contrary to item description, this item always increases the speed by %

Upgrading
In order to upgrade a Held Item to the next level you need doubles. Flat stats improve your pokemon from level 0, while skill buffs apply starting from level 3.