From Destinypedia, the Destiny wiki
Ascendant Alloys are required to add Enhanced Perks to craftable weapons.
They can be acquired through Nightmare Containment, The Witch Queen weekly campaign missions, The Wellspring on Master difficulty and purchased from Rahool pnce per week in the Tower for 400 Legendary Shards. One Ascendant Alloy is also available for reaching reputation rank 16 with Banshee-44.
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