Lore
Kalli is one of the three Techeuns that was taken by Oryx during the attack on his dreadnaught in Destiny 1. We need her help to defeat Riven, so like Sedia in the Corrupted strike we need to free her from taken influence by defeating her.
Mechanics
To complete this encounter you need to defeat Kalli before she kills you. The main way she does this is by “conceiving an ontological weapon” and wielding it against you. It is an instant kill on any guardian that isn’t safely inside one of the doors that open under Kalli right before she wields her weapon.
Only one guardian can be inside each door, so six doors must be opened. This is done by standing on the plates in a rough circle around the outside edge of the arena. There are nine plates, six of them will open doors and three of them summon ogres in the center of the arena.

Each plate has one of four symbols above it. Three of the symbols will appear in pairs above inner arena. The four possible symbols are as follows:

Eight Snake

Split Snake

U Snake

Infinity Snake
The three symbols hung in pairs indicate which plate to stand on. Each outer plate will open three doors in the section under the matching inner symbol pair. When a matching plate has been successfully cleansed, one of the hanging symbols in the center will disappear.
To cleanse one of the plates a guardian must stand on it until a taken knight appears and then kill the knight. To complicate this, two of the three sections of the plate are slowly taken until they explode, killing any guardian standing in the taken portion. After the explosion the un-taken section will change and two different sections will begin to be taken. While the plates are active, taken thrall spawn throughout the arena. Kalli will also randomly visit the plates and attack the guardians. Shooting her in the head will make her leave.

After the plates have been cleansed, Kalli will appear under one of the pairs of symbols. She will attack the guardians and begin to summon her weapon. Shortly after the text “Kalli prepares to wield her weapon” appears on screen, the doors will open in section underneath her. Everyone has a few seconds to get inside an unoccupied room before Kalli uses her weapon. The doors will then open and Kalli will move to underneath a different pair of symbols. While the guardians are shut behind the doors, taken psions will spawn in the center of the arena.
After Kalli has appeared under each pair of symbols and used her weapon each time, she will return to roaming the room. At this point the plates reset and must be cleansed again to open the doors. The inner set of hanging symbols may change, requiring a different set of plates to be cleansed.
Strategy
Kalli is a realtivly simple encounter that serves as a good check on communication and damage output. If it takes more than two DPS phases to deafet her, your fireteam might struggle to do enough damage to complete later encounters.
Phases of the Fight
Plates Phase
Determine which six plates need to be cleared by looking at the inner ring of hanging symbols.
Cleanse the six plates and kill the knights.
DPS (Damage) Phase
Do the following three times:
Go to the center and damage Kalli as a team.
Hide in the rooms to avoid the wipe mechanic
Return to the Plates phase and repeat until Kalli is defeated.
Loadout Suggestions
In general it’s best to have a way to apply a debuff for extra damage, a way to avoid reloading weapons, and high damage dealing supers. The following suggestions are few good synergies.
Use Tractor Cannon or Hammer Strike/ Melting point. Tractor Cannon has better uptime, but the damage buff is only equal to Hammer Strike when using void. It pairs well with Hammerhead and Crooked Fang-4FR.
Hand cannons and shotguns work well for cleansing plates
Lord of Wolves, Prospector, Thunderlord, and Hammerhead can all deal a large amount of damage to Kalli.
Hunters should use 3 shot Golden Gun with Celestial Nighthawk.
Warlocks should use Well of Radiance with Lunafaction Boots. Use a rally barricade if Lunafaction Boots aren’t available. If there are more than three warlocks running Well of Radiance, Chaos Reach with Geomag Stabilisers are a good option for the additional warlocks.
Titans should use Hammer Strike or Tractor Cannon so hunters and warlocks are free to use their supers in the center.
Tips
Assign each guardian a door/room that they will go to. A simple way is to assign each guardian a number 1-6. When the doors open, the first door starting from the top-left and scanning accross left-to-right, top-to-bottom, is door one. The next open door is door two and so on.
If there are multiple warlocks, assign each one to place Well of Radiance at different times durring the DPS phase for maximum uptime.
After the doors open, have 1 or 2 guardians throw a grenade into the center to destroy the taken psions. Make sure to pace out your grenades so there are enough for all three parts.
Challenge: Summoning Ritual
This challenge requires you to summon and kill three ogres in addition in completing the encounter. The ogres are summoned in the center of the arena when a guardian cleanses one of the three plates that don’t match one of the symbols in the center.
Because of a bug where the third ogre doesn’t appear if there are already two in the center.