Stardust Fragments are a Hardmode post-Lunatic Cultist crafting material. It is one of the four Lunar Fragments, dropped from the Stardust Pillar during the Lunar Events. The Stardust Pillar drops 10-60 fragments on normal mode, and 18-90 on Expert mode. These fragments can be used to craft a lategame armor set that benefits all summon weapons, and can be used to create its respectively themed tools, weapons, wings, etc.
Crafting all of the Stardust gear, weaponry, and tools requires 121 Stardust Fragments and 68 Luminite Bars (272 Luminite).