This quest will begin when Dean Grundir introduces you to a scholar named Octavius - this means it is a follow-up to the events of the "On the Right Path" main quest.
The dean introduced you to a scholar named Octavius. Help him with the preparations for his experiment.
Reward: Abyss Artifact x1
The experiment will take place the following day. You can use the "Wait" option to skip directly to the correct time. When you return to the spot, Octavius will begin the experiment after a short speech.
Your first task will be to activate the lock device switch underground. To reach the lower level, head to the right side of the dome (northeast).
There, you will find stone stairs that you can use to descend.
Once you've headed down, locate the hatch, which looks like a small wall panel consisting of nine plaques. Examine it.
You now need to solve a puzzle. You must press the plates in the correct order so that all of them light up. One of the solutions to achieve this goal is to press the plates in the order shown in the screenshot below.
Once all the buttons light up, the hatch will slide away, revealing a lever that you can pull.
This will cause the dome to open, allowing you to proceed to the next task - insert the batteries to activate the device.
Return to the upper level. There you will find four pillars with cubic openings and cubic batteries - they are marked on the map.
You must do the same for each of them - Use Axiom Force to grab the cube - this is the battery - and place it in front of the opening in the pillar. When the battery is in the correct position, it will begin to shimmer green and you can use the Force Palm to push the cube into the slot in the pillar.
Once all four batteries are in their slots, Octavius will begin the next phase of the experiment - it will not go according to his plan, and you will have to intervene - Use Axiom Force to remove the unstable core. Aim at the blue orb in the middle, then pull it out the core.
The experiment will end in a failure. Octavius will be sucked into the portal, and after a moment, a new threat will appear - the magic boss named Tenebrum. You next task will be to defeat it - Approach Tenebrum / Use Force Palm to subdue Tenebrum.
The fight will begin with a prompt to press the correct button combination.
Once you've done that, you will receive instructions on how to use Blinding Flash...
...which you must use to expose the enemy's weak spot.
The open dome creates a strong upward air current. To reach the boss, you must double jump and deploy your wings to catch the wind. This updraft allows you to hover and maneuver through the air, which is essential since Tenebrum remains at a high altitude and cannot be reached by standard ground-based attacks.
The primary way to damage Tenebrum is by using Force Palm while flying. Because the boss moves erratically, timing is everything. It is most effective to wait until he moves toward the center of the arena to charge a heavy attack. During this window, close the distance and strike.
Be cautious of his attacks / projectiles! If you are hit mid-flight, you will be knocked out of the air and suffer fall damage upon hitting the ground.
Force Palm relies on Spirit and if that runs out, you will need to descend to the solid ground around the perimeter. Use the stone pillars as cover to protect yourself from incoming spells while you manually recharge your Spirit meter.
After defeating Tenebrum, another cutscene will begin. Dean Grundir will ask for your help in investigating the strange phenomenon and give you the Spire of the Stars key. You don't need to do anything to receive the Abyss Artifact - just wait. After that, this quest will end and the next one will begin.
Octavius had embarked on a perilous endeavor, seeking to create an unknown power through the clash of two titanic forces. Though urged by all to stop, his persistence led to a catastrophic blast that pulled him into its very center. It took a desperate battle to finally excise the black corruption that emerged.
