An Xyz monster (pronounced ik-seez), is the newest kind of card. They are placed in the Extra Deck. Like Synchro Monsters, they are special summoned in various ways by controlling the specified cards, then using them as Xyz Materials
An Xyz Summon is a method of summoning an Xyz Monster by moving the Xyz Materials under said Xyz Monster. The materials remain on the field, "Attached" to the Xyz Monster by being overlayed under the monster. Materials overlayed are generally used as the cost for the XYZ monster's effect(s).
Cards whose effects are triggered when it leaves the field, such as Sangan and Reborn Tengu do not activate, as monsters used for Xyz Summons do not leave the field when used for an Xyz Summon, but are not considered a part of the field while attached to an Xyz monster.
Xyz materials are not considered monsters while attached to the Xyz monster, nor are considered monsters while detached. Therefore, Dimensional Fissure will not banish Xyz Materials sent to the graveyard.
Xyz Monsters are not affected by cards which designate Level. For example, due to the lack of a level, Xyz Monsters are unaffected by Level Limit - Area B or Gravity Bind, and CAN attack. Additionally, cards whose effect increase or decrease the levels of monster(s) cannot be used on an Xyz monster