Weapon crafting has been introduced in Destiny 2's newest expansion The Witch Queen, allowing for robust customization of gear. To know more about the system, you can read up on it in our Destiny 2 weapon crafting guide.
The main takeaway is that you'll need several resources to shape and reshape weapons, the majority of which are easy to acquire from various world activity sources and extracting the materials from qualifying weapons. But one weapon-crafting resource that is fairly rare is Ascendant Alloy, which is used to craft enhanced perks on guns. Currently, Ascendant Alloy can be found from a handful of sources, and only one makes them easy to get--if you have ample Legendary Shards to burn on them.
