Advent Condition (降臨条件 Kōrin Jōken) is one of the condition required to play a Z/X Extra card. It is associated with the Dingir, although non-Dingir cards occasionally have it as their condition as well.
Advent Condition basically modify how a card is played. Instead of paying its Cost as usual, the amount of cards in the player's Resource simply have be equal to or greater than the Cost of the Z/X Extra. Also, they must destroy their Reboot State Z/X on Square that fulfill the criteria listed in the Advent Condition, with the total of their Cost being equal to or greater than the Cost of the Z/X Extra as well.
1019 Advent Condition
1019.1 "Advent Condition" change the required compensation in order to play a Z/X Extra as that card is played.
1019.2 Advent Condition is written in text or subtext as "Advent Condition : [compensation]". When a player plays a Z/X Extra with Advent Condition, that card is played without paying the Resource Cost if the amount of cards in the Resource of player that play the card is equal to or greater than the Cost value of that card, and by destroying a number of Reboot State Z/X designated in [compensation] with total of their Cost value equal to or greater than the Cost value of that card.
1019.3 When Z/X are destroyed as compensation to perform Advent Condition, those Z/X are not destroyed by ability or effect.