History of Kell Echo

The Kell Echo is the final boss of the Prophecy dungeon, from Season of Arrivals. It is a Taken Echo, a manifestation of a Fallen Kell created by the Nine, built to test Guardians on wielding Light and Darkness together.

In the fight, three clones surround the arena; collecting Light and Darkness motes lowers their barriers and forces them to retreat. The real boss then fights in a fragmented hallway with an energy field, modified Darkness Bolt attacks that teleport players backward, and Taken support. Some in the community read it as foreshadowing Eramis and Stasis (Destinypedia's interpretation). The related activity is Darkest Before.