The Keystone Citadel - Concerned Monk | Side quests Lords of the Fallen Guide

The Concerned Monk.

After you clear the Planetarium, right next to the entrance to that location, on the right, you can talk to the Concerned Monk [M5.6]. He asks you to find his brother.

The monk's brother enclosed in a cocoon.

Go towards the secret room #1, to find the missing brother. Locate the mysterious symbol on the floor and run ahead, for a moment, to enter the door that is temporarily unlocked. Defeat a Spider, and interact with the hanging cocoon [M5.10]. This way, you will obtain the Key to the Citadel basement. Take the key to the Planetarium and talk to the Concerned Monk again, and you will receive 4500 EXP.