Ignition Overdrive (イグニッションオーバードライブ Igunisshon Ōbādoraibu) is the ability to use multiple Z/X at the same time.
From gameplay perspective, Ignition Overdrive instead refer to the particular game mechanic that allow a player to play a card without paying its Cost, and possibly in multiple quantities.
Z/X Encyclopedia Entry
During the Ignition Phase, the turn player may choose to perform Ignition by following the procedure below.
- Choose a card from your Charge and put it into Trash.
- Reveal the top card of your deck.
- If the revealed card has an Ignition Icon, you may play that card without paying its Cost. If it is not played or does not have an Ignition Icon, put that card into Trash.
Similar to the story, this process is called Ignition (イグニッション Igunisshon) while the act of playing the revealed card is called Overdrive (オーバードライブ Ōbādoraibu). Ignition can be performed as many time as long as the the player has enough cards in his or her Charge, and thus, it is possible for a player to play multiple cards without paying their Cost and gain tremendous advantage.
Card abilities or effects may also instruct a player to "perform Ignition". In that case, that player perform the Ignition process as usual without putting any card from his or her Charge into Trash.
Some card possesses the Ignition Icon (イグニッションアイコン Igunisshon Aikon) on the left side of the card name, which is shaped like a stylized dragon head (a possible reference to the originator). All cards with this Icon can be played without paying their Cost if revealed during Ignition.
Other than cards with "natural" or printed Ignition Icon, a small number of cards also possessed an ability or effect that gives them Ignition Icon on certain condition. Certain abilities or effects like Zero Optima may also specifically refer to cards with Ignition Icon.
- Z/X Encyclopedia (Japanese)