Infusion

Infusion, a feature introduced with The Taken King, is the boosting of the Attack or Defense rating of a favored Weapon or Armor piece, a mechanic similar to the use of Etheric Light. Infusing a stronger Light-leveled piece of gear into another less powerful one will have the level increased to that of Infused piece, but will not receive any of the perks, allowing for players to choose armor or weapons for aesthetic reasons and still have good "rolls", or perks they like or want.

In Destiny, only Weapons and Armor from Year 2 and Year 3 are able to be Infused. In Destiny 2, all Legendary and Exotic gear is Infusable and requires only a quantity of Glimmer and Legendary Shards; if a Rare item is being Infused into a Legendary or Exotic item, 4 units of Legendary Shards are required, but if a Legendary item is being used for the Infusion instead, it costs only 1 unit.