Lux Enhancement Shards are items used to enhance Exitum Lux Armor. Them and their accompanying armor set can be bought from Nuba if Abaddon, Araghur, and The Lost Siblings have been defeated in True Mode. Upon being bought, they have a randomized effect, each based on a damage type depending on the color of the shard. They also drop rarely from enemies after defeating the Lost Siblings. Randomized "Big" Lux Enhancement Shards can also be obtained by trading with Neil.
Lux Enhancement Shards are added to the armor in Nuba's True Mode exclusive "Assemble Armor" UI. Additionally, they can be dismantled into Lux Shard Dust in the aforementioned UI, allowing you to re-craft them with a new effect for 5 of the respective shard types' dust.