At the Goddess Palace you can use Dim Star Sand or Bright Star Sand to summon Myth Cloths. After every 10 uses of Dim Star Sand you can claim 1 Bright Star Sand at the exchange at the top right corner. Using Dim Star Sand will have a small chance to summon a Myth Cloth, but Bright Star Sand have a guaranteed 100% chance to summon a random Myth Cloth.

This guide is sourced from yabusame.