Xyz Material

Xyz Material Monsters (pronounced ik-seez, エクシーズ素材, Ekushīzu sozai, known as Overlay Units in the anime), are the result of monsters being used in an Xyz Summon. When an Xyz Monster is Summoned, the monsters used in the Xyz Summon are stacked underneath the monster instead of being sent to the Graveyard (referred as being "Overlaid" in the anime), and so only one Monster Card Zone is occupied. Xyz Material Monsters are essential to Xyz Monsters as in most cases they are used for a card effect, such as that of "No. 17 Leviath Dragon". Removing an Xyz Material Monster for the effect of an Xyz Monster is referred to as 'detaching'. If the Xyz Monster is destroyed or removed from the field, any associated Xyz Material Monsters are sent to the Graveyard. When an Xyz Material Monster stacked under an Xyz Monster is removed or detached, it is sent to the Graveyard. Removing all of the Xyz Material Monsters associated with an Xyz Monster can have negative consequences, as in the case of "Number 39: Utopia". Xyz Material Monsters underneath Xyz Monsters do not count as monsters, or as being on the field.

In Yu-Gi-Oh! ZEXAL, Xyz Material Monsters are depicted as orbs of light colored the same as the Xyz monster's Attribute, which orbit around their respective Xyz Monsters. Also, during an Xyz Summon, the Xyz Material Monsters' corresponding Attributes light up their bodies.