“A mysterious rune. Its aura matches those of the planeshifting Hive who periodically appear on the dreadnaught.”
Hunt down the hidden Taken threats 0/7
Enter the Mausoleum and look forward toward the bright light at the far end. This is to the left of the Rupture, opposite the cabal ship.
Turn to the left and head through this doorway.
When you are inside, head through the doorway leading to the Founts. Head straight forward toward the gate.
To the left before you reach the gate.
Enter the hallway and turn to the left. Head forward until you find the hole in the ground. Drop down into it.
Head down the hallway and turn to the right. Go toward the small hole at the far end. Go through this hole in the wall.
Once through, look to the left. You will find the chest that activates an event.
Follow the directions to reach the event. Then follow the prompts on screen. It helps to have a Fireteam because of the number of enemies you will need to deal with.
When you have defeated the boss, a chest will appear in the middle of the area. Open it to claim your Calcified Fragment.
You will need to re-kill the bosses you killed to charge the rune. After them comes a Zealot Champion. Defeat it and open the chest with the Charged Agonarch Rune. This will give you Calcified Fragment 36