Kell Echo

The Kell Echo is a Taken projection of a Fallen Kell. It was conjured by the Nine as a obstacle to show The Guardian that, by using the Dark and Light Motes together, their combined power is the means to survival in the battle against the Darkness.

The Echo is encountered as the final boss of Prophecy dungeon.

Gameplay
After a final approach with the Taken Probe, the Guardians' nemesis, the Kell Echo, reveals itself and begins to engage its assailants, along with two squads of Taken Psions and two Knight Echoes.

On all three sides of the room, a copy of the Kell Echo will stand in front of one of the paracausal founts. Like all other previous encounters, players should, once again, neutralize any frustrating add, position themselves out of harm's way and kill a Knight Echo for their motes. After acquiring a total of five motes and dispersing the correct pillar of energy, the clone should attempt to escape to the center of the room, removing one threat from the room and giving the players a step closer to a damage phase. However, once the copy of the Echo flees, a Devoured Ogre will spawn and begin to rapidly assail the Guardians, so it should be quickly disposed of before it proves to be too much of a threat.

Once all three copies are forced to retreat and all adds are killed (a recommendation before moving on), players should meet in the center triangle in the room, where they will be pulled into the floor and brought through a strange tube before finally finding themselves within a massive fragmented hallway from where the Kell Echo should be seen directly ahead.

Here, the Kell Echo brings two new mechanics to the table. One is a protective field surrounding the Echo that prevents players from suffering the effects of Dark Entropy, which instantly kills a player once it stacks up to 10. The other feature is a modified Darkness Bolt ability that, instead of blinding normally, teleports players a few platforms back from the carnage while exposing them to the Dark Entropy debuff, so it should be avoided at all costs. Death here severely mitigates the damage done to the boss, so Guardians should always be on their toes, staying within the protective aura of the Echo and avoiding its Shrapnel Launcher and its Taken Hobgoblin sniper back-up.

After a while, the Echo will begin to retreat to a platform or two behind it before finally teleporting to the end platform, where it will briefly stay before finally retreating to the tetrahedral arena, thus ending the damage phase. The encounter ends once the Kell Echo itself is neutralized, where players will then be brought before the Emissary, be given the answer on the nature of the Darkness, as well as a reward and powerful gear once the Dungeon is finally complete.

Trivia

 * The Guardians using both Light and Dark Motes to defeat the Kell Echo is a precursor to the storyline introduced in Beyond Light expansion, where the Guardian acquires the power of Stasis.
 * The Kell Echo's design is currently unique to them, with a helm that looked like a combination of Aksor, Archon Priest's, and the Kellslayer's Helm.
 * If the Kell Echo's body is observed after their killed and their Taken eye disappears, they can be seen wearing a veil obscuring their face.
 * The Kell Echo can be seen traversing the dungeon, teleporting away from the Guardians from facing it in the Entrance to the Phalanx Echo fight and the Hexahedron to the Deadsea encounters.
 * Occasionally the Kell Echo will not warp away from the Phalanx Echo arena, staying for the entire encounter. However the Kell Echo does not engage in the fight in any way.

List of appearances

 * Destiny 2
 * Season of Arrivals