“Under Saarthal” is a College of Wintergold Faction Quest in The Elder Scrolls V: Skyrim
Saarthal is found to the Southwest of the College of Winterhold. The part of the mountains it is found has a good size wolf population and other threats like bears and Frost Trolls. If you can fast travel there, expect to wait a while for the others to show. They will gather at entrance. Talk with Tolfdir to move the group inside. Tolfdir will explain some of the history of Saarthal. He will eventually ask the Dragonborn to seek out Arniel Gane.
Head on down the ramps to the ground level. Once there turn to the North and head down the corridor there. Keep to the stone bridges and follow them down to the lower level. Go to the Northwestern section of them then look to the North to find the ramp down. Follow the Bridge to the South then follow the passage to the West then North. This will lead into a tunnel. Follow it North to find Arniel Gane in a chamber just to the West.
Arniel will ask the Dragonborn to explore the chambers to the North. The Dragonborn is now looking for 3 or 4 Magical Artifacts. One items is found to the Northwest of him: a Magic Ring. This sits on the floor:
A second is to the South of the ring:
Head to the Northeast now. This will take you into another portion of the chamber. Look to the corner to the Northeast. This will lead you right to the third Artifact:
Go across the room to the Northwest now. You will find a well lit area with an Amulet hanging on the wall:
Taking the amulet will drop bars behind the Dragonborn, blocking their path back. Tolfdir will come over to the Dragonborn and explain a bit about things. He prompts the Dragonborn to think about how to use the Amulet to escape the area you are in:
Once that is resolved. Head over to Tolfdir and talk to him. This will get him moving and he will go through the doorway that has just been opened by the spell. Follow him down the passage for a while. This will lead to a room with a table in the middle:
Wait in here for a moment. The Dragonborn will be contacted directly by a projection of Nerien:
He will explain that the Dragonborn has set into motion an irreversible chain of events. The Psijic Order will judge the Dragonborn based on the actions that they take during this course of events. After the talk, time resumes around the Dragonborn. Talk with Tolfdir about the contact. After that there are a few Draugr that need to be dealt with. Destroy them then head through the door to the West. Turn to the North and head down the slope there. A gate will be blocking the path forward. Look to the right of it to find a lever that will open it.
Continue to follow Tolfdir as he goes deeper into the area. The next chamber has a number more Draugr. All of them need to be dealt with for the bars to retract that block the path forward. Tolfdir will leave you after this room is cleared.
Go over to the barred gate and look to the left or right of it. Either side you will find a chain that will retract the Spikes or open the door. The chain to the right will open the door. The chain on the left will retracts the spikes. Head over to the door and go inside to reach the next area.
Head straight in to the East. Expect yet more Draugr as you make your way North into the Ruins. Be very careful as there are a lot of traps in this area. Look at the floor for discolorations or raised areas. Continue forward and go up the stairs you will find on the right. Turn left at the top of them and head over to the raised Sarcophagus. Inside you can find a weapon. After that just go through the Iron Door to the East of it. Turn Northward through the corridor and head downward. be careful approaching the chest at the bottom of the slope as there is a trap stone nearby it. Just grab the contents and keep moving to the North. You will arrive in a corridor with the next puzzle:
Head on through the door that is opened by solving the puzzle. Go forward and through the Iron door ahead of you. Inside this next room there are Draugr Wights to be dealt with. Go through the door and you will arrive in a large room. This houses the next puzzle:
Head on through to the South after that. Go down the slope and head West into the next room. Be careful as there are numerous traps on the floor. Head to the South in that room then West and go through the Iron door there. Inside this room a massive orb. Look down to the floor below and you will find a Draugr that stirs from its throne. This is Jyrik Gauldurson.
When the battle starts, do not attempt to engage Gauldurson. Until Tolfdir interacts with the Eye of the Magnus, he cannot be harmed! After that has been done then begin attacking this Draugr with everything you can.
After the fight, talk with Tolfdir. He will send you back to the College to talk with Savos Aren, the Arch-Mage. Head on back and talk with Savos. He will tell you to start researching the object to learn more about it and begin the next quest.