Infusion

Infusion raises a weapon or armor piece's Power by dismantling a higher-Power item of the same type into it.

How it works

Per the Destiny 2 Wiki, the dismantled item's level transfers to the kept one. Only Legendary and Exotic gear can be upgraded, but any rarity can be dismantled into it, and items must match (a Kinetic weapon with a Kinetic weapon, gauntlets with gauntlets). The classic cost was an Upgrade Module from Banshee-44, or 1,000 Glimmer for a duplicate. Legendary gear from before Season of the Worthy was subject to an infusion cap.

Caveat

That description reflects older versions of the game; infusion costs and caps have changed over time, so check the current rules in game.