The methods for buying these filaments shifted significantly over the franchise's history: :

In modern Destiny 2 (post-Season 19), planetary materials like Helium Filaments have been deprecated.

Players could buy them at the from the Vanguard Quartermaster or Crucible Quartermaster .

You can no longer buy them to use for upgrades. Instead, any leftover stacks in your inventory can only be "sold" to at the Tower for small amounts of Glimmer. Historical Context and Usage

: Described as filaments of helium-3 fusion fuel, they were canonically gathered from lunar regolith and used to power everything from individual fusion rifles to the Last City itself.

They were often sold in batches of for 1 Legendary Shard or 5,000 Glimmer . Current State (Deprecated) :

While you can no longer buy them for functional use, they remain a nostalgic symbol of the Moon's "grind" for veteran Guardians.

In their prime, Helium Filaments were more than just a currency; they were the "fuel" for progression.