Xyz Summons can be conducted when there are two or more monsters of the same Level on your side of the field. Those monsters can be used as Xyz Materials to Summon an Xyz Monster whose Rank is the same as the Levels of the monsters used.
In order to Xyz Summon an Xyz Monster, you must first take the required Xyz Materials face-up on your side of the field and stack them together (called overlaying in the anime). Then, the Xyz Monster is Xyz Summoned from your Extra Deck, and placed on top of the stack.
The respective battle positions of the Xyz Materials do not matter, so long as they are all face-up. However, once you have Xyz Summoned your Xyz Monster, ensure that the entire stack is neatly aligned in face-up attack position, regardless of whether or not the Xyz Monster is summoned in face-up ATK or DEF position.
An Xyz Summon is a type of Special Summon, and an Xyz Monster is a Special Summon-only monster.
Some effects may require you to remove Xyz Materials from an Xyz Monster. In this case, the required Xyz Materials are taken from beneath the Xyz Monster in question and sent to the Graveyard. This is known as detaching. Be wary though, as some such effects may have a downside if an Xyz Monster has no Xyz Materials left beneath it.
Note that an Xyz Monster Special Summoned via any means other than an Xyz Summon (except for Xyz Reborn) will not have any Xyz Materials beneath it. Therefore, any negative effects that might apply to an Xyz Monster in such a state will be applied immediately.
If an Xyz Monster is flipped face-down, the Xyz Materials beneath it are not sent to the Graveyard.
If a card that would banish cards sent to the graveyard (such as "Macro Cosmos" or "Banisher of the Radiance") is in effect, when an Xyz Monster is destroyed/removed from the field the Xyz Materials beneath it are banished. However if an effect that would banish a monster(s) on the field (like "Dimensional Fissure") is activated, only the Xyz Monster will be affected. The Materials used will be sent to the Graveyard.
In the anime, when a "Number" Xyz Monster is Xyz Summoned, a galaxy-like gate appears in which the Xyz Materials (in a energy form) transfer into. The gate explodes, and a Numbers' sealed form appears and unveils itself into its artwork. When a non-"Number" Xyz monster is Summoned, a red colored spiral portal is used instead. The Xyz Materials then turn into orbs of light which surround the Xyz Monsters who absorbs them when the player detaches them. This idea of a galaxy is derived from Konami's statement of the Xyz Monsters coming into our universe through a black hole. In Yu-Gi-Oh! 5D's Tag Force 6, all Xyz Monsters are Xyz Summoned through the red spiral portal.
Similar to how players say that they "Release"/"Tribute", "Sacrifice", "Fuse", or "Tune" their monsters to perform a Tribute, Ritual, Fusion, or Synchro Summon, players would state that they "Overlay" their selected monsters to perform an Xyz Summon.
How to Xyz Summon
- When Xyz Summons were revealed in the OCG, they were mistakenly translated as "Exceed Summons" by fans. Many translators acknowledged after the official term was revealed that "Xyz" was also a valid translation, but that they assumed it was not correct during the initial translation since it does not have any obvious pronunciation. The fact that it was meant to be pronounced "ik-seez" was not obvious from the katakana "エクシーズ", which has a romaji reading of "Ekushīzu" and the closest English equivalent to it was "Exceed".