In order to fully experience everything in your new Prismatic subclass in Destiny 2: The Final Shape, you'll need to hunt down every Prismatic fragment scattered across the Pale Heart patrol zone. While you can find your alternate supers, grenades, melee attacks, and aspects by completing the campaign and the ‘Lost in the Light’ and ‘Found in the Dark’ quests, the Prismatic fragments require a lot more time and effort to unlock.
Each one is scattered across The Pale Heart, sat in a chest hidden in the environment...