Online:A Walk Above the Clouds

Quick Walkthrough
# Talk to Veldrana, and help her light a fire.
# Find the cult cell leader.
# Collect the components and perform the ritual.
# Find and defeat the dragon priest.
# Talk to Centurion Andrin at Forelhost's base.

Detailed Walkthrough
Near Forelhost, you find Radrase Alen's body. It looks like she was a Worm Cultist who was mauled to death by sabre cats. Inside her pack is a journal. 
:''"Nordahl showed us the shard of Wuuthrad tonight. It was very impressive! He's shown great cunning to find it. Our brothers and sisters scour the Smokefrost Peaks looking for Ysgramor's legacy."
:; 
:"He told us his plan to ascend Forelhost, and search the crypts of the Dragon Priests. There was muttering in the ranks. Cowards. Why should we fear the dead? They are like toys to the likes of us!"''

Close the journal to see yourself almost meet the same fate. Defeat the sabre cat, then continue up the path to search for the shard. As you ascend, the ground starts to freeze, and you come across Veldrana huddled close to a fire for warmth. She was tracking the cultists for King Jorunn, but she was attacked bat sabre cats and ran out of wood. You tell her you'll gather kindling for her, and she tells you you'll need to stay close to the fires to survive and warns you about the sabre cats.

You need two pieces of kindling. These look like groups of sticks. The closest one is behind a pine tree up the snowy hill to the north. Activate the kindling, and take both kindlings. Return to Veldrana, and light the campfire.

Talk to her as she warms up. She thinks the cult left their leader (along with the shard) on the top of the mountain. 

Run north to the small building and the ladder to Forelhost. Exit through the southwest opening, and run quickly to the fire. You see Nordahl's body; he appears to have been clawed by a human. Examine the Worn Grimoire next to him, then read Practical Necromancy. It tells you how to summon a spirit of Aetherius. 
thumb|right|The ritual circle

You need to follow its instructions and start by collecting animal hide, nightshade and an animus geode. In a burlap sack at the next camp, you find crushed nightshade. Inside the tent near the third and fourth bonfires, the animus geode is inside a broken crate. The animal hide is in a backpack at the sixth bonfire.

Now it is time to perform the ritual. Nordahl's summoning circle is to the left of the tent where you found the geode. You need to light the candles according to the order in the grimoire: east, west, north, then south.   

Use the ritual bowl, place the hide on the pike, then use the animus geode. You have just summoned Nordahl's spirit. Talk to him. He came to the mountain seeking a Dragon Priest mask. His cultists died to draugr and never even saw a Dragon Priest. The draugr took the shard and locked the door into the temple.
Temple Door Puzzle
You need to solve an ancient puzzle before you can enter the temple. There are three carvings around the temple, showing hints to the solution. The puzzle hints are that each image is used once, the snake is in the center, and the right pillar "has plumage." The center pillar is in front of the fire and should already be set to snake. The right pillar needs to be turned once to eagle and the left pillar needs to be turned twice to whale. The solution from left to right is Whale, Snake, then Eagle.

Enter the temple, and look for the dragon priest. He's not in the temple, so continue through to the door to Forelhost Peak.

Make sure you gather kindling from the ground near the tree when you exit. Continue to an open area and a sarcophagus. Light as many bonfires around it as you can as soon as possible. Then activate the sarcophagus to trigger the fight with the Dragon Priest Vosis. When you defeat him, the shard of Wuuthrad floats around the center of the sarcophagus. 

Before you return to Veldrana to complete the quest, make sure you collect the Skyshard at the top of the mountain, southeast of the sarcophagus.

Head back down the ladder, and talk to  Centurion Andrin in the middle of the path.

Notes

On some builds it will be best to maximize your Health capacity with food and/or with jewelry that has the Healthy trait, and/or to equip jewelry enchanted to increase Health regeneration, especially when you arrive at the start of the path toward the altar of the Dragon Priest at the top of the mountain. Your character also loses less Health from the cold if you sprint while away from a fire, and your Health will recover fully in less time at the next fire.
Completing this quest is not necessary to reach the Skyshard. However, the only path to the summit is through the Forelhost Crypts, so you must accept the quest in order to unlock the crypt doors. This can be done by following the path lit by torches, which function identically to the player-lit fires and to regain Health. At the summit, you can then sprint past Vosis' altar and reach the Skyshard with sufficiently high Health.
Alternatively, if you are in a group, only one member must accept the quest in order to unlock the Forelhost Crypts doors and gather kindling with which to light the fires.
If you do complete the quest, the doors to the Forelhost Crypts subsequently remain unlocked, so you can return to the summit if you missed the Skyshard.
 

Quest Stages