History of Dark Entropy

Dark Entropy is a debuff from the damage phases of the Prophecy dungeon's final boss, Kell Echo. During those phases, Kell Echo periodically teleports backward and emits an aura, and Guardians standing outside that aura gain stacks of Dark Entropy; staying inside the ring prevents new stacks. A hit from the boss's Taken energy attack teleports the player back to the starting platform, which can build stacks quickly. Blueberries reports that a player dies at 11 stacks, while other guides cite 10.