Lux (ルクス, Rukusu?) are particles of light that appear in Kingdom Hearts χ. They are gained by defeating Heartless and are used to rank players on a weekly basis, resulting in the availability of more prizes, which increase in rarity depending on how much Lux has been collected.
There are several factors that can influence the amount of Lux that is collectable. Every assist card the player uses increases the drop rate of Lux by a small amount; this depends upon the used assist card's level. Each day a number of "Lux Up Time" occur and while these periods last the amount of Lux earned when the Player defeats Heartless automatically doubles.
The Lux determines all regular rankings in the game. All Lux collected during the week by the Player sets his or her individual rank while the amount gathered by the whole Union sets the Union's place in return. The team that collects the most Lux during the day wins the daily team battle.