Event (イベント Ibento) is one of the card types in Z/X - Zillions of enemy X- TCG. As the name suggest, they represent various "event" that happens in the story of the game.
Event cards are single-use cards with various effect that able to affect the gameplay (e.g. deal damage to Z/X, draw cards, increases Power, etc.) and act as the support for Z/X. They are also the only cards with the Event Ability (イベント能力 Ibento Nōryoku), which is performed when the Event is played.
Event cards can be played during the Main Phase of your turn, or during the Battle in either player's turn. When an Event is played, it is placed in the Temporary zone before it was put into Trash after its effect has been resolved.