Bloodmoon:The Ristaag

Quick Walkthrough
# Speak with Korst Wind-Eye in the Skaal Village and agree to perform the Ristaag. 
# After nightfall (around 10 pm) find Rolf Long-Tooth a little ways west from the northern tip of Lake Fjalding. Speak to him to learn the details of the hunt.
# Wait by Rolf for a bit and investigate the disappearance of Sattir. Find his body behind some rocks just to the southwest.
# Follow Rolf for a bit and investigate the disappearance of Grerid when he asks. Find her body behind some rocks to the east.
# Follow Rolf some more and you will shortly be attacked by three werewolves. Kill them and speak with Rolf. 
# Wander around until the Spirit Bear appears and kill it.
# Return with the heart of the Spirit Bear to Korst in the Skaal Village.

Detailed Walkthrough
Return to Skaal Village
After returning the totem, the Shaman Korst Wind-Eye will ask you to perform the Ristaag, a ritual hunt that is meant to bring favor from the All-Maker on the Skaal. You are to meet at night-fall, along with Rolf Long-Tooth, who is on the western shore of Lake Fjalding. The directions, again, are slightly deceiving, as Rolf is far west from the western shore at the very northern end of the lake (coordinates -172145, 196843, 1112; if you see a second river, you've already passed him). Around 8pm is the earliest time you are able to talk to him and go on with the  quest. They are in a slightly elevated snowy forest area carrying torches, and Long-Tooth is in the middle.

The Ristaag
Rolf explains the ceremony which involves hunting the Spirit Bear summoned by the Totem of Claw and Fang you recovered. The bear must be slain and its heart returned to Korst before daybreak or the ceremony will not succeed. You are to follow and protect Rolf during the hunt. After this you will wait with Rolf for a short period before you hear a bone-rattling roar. Rolf will tell you that it came from Sattir the Bold's path and asks you to investigate it. Explore just to the Southwest of Rolf and you'll find Sattir dead behind some rocks (coordinates -173998, 194749, 677). Return to tell Rolf of the matter.

The Hunt
Rolf will now take off towards the south so follow him. After a short jaunt you'll hear another scream and Rolf will ask you to check on Grerid Axe-Wife. Turn to the east and check behind some rocks to find Grerid's corpse (look for her torch light) (coordinates -167780, 193467, 233). Return to Rolf with the bad news. He will lament the loss but continue on with the hunt. Seeing as you and Rolf are the last two on the hunt, you should be on your toes. After a short time you will be suddenly attacked by three werewolves so have your weapon and healing potions ready. Speak with Rolf after the attack and he'll be so impressed that he asks you to lead the hunt for the Spirit Bear. 

The Spirit Bear
Since Rolf has now asked you to lead the hunt, its up to you to find the Bear, although you have been given no real hints on where to find it. Continue in the direction Rolf was walking, and after a short time the Spirit Bear (which is white) should appear near you. Kill it and take the heart from its corpse. Speak with Rolf again who will tell you to return the heart to Korst alone.

Return to Korst Wind-Eye
Return with the heart of the Spirit Bear to Korst in the Skaal Village. Korst will congratulate you on the hunt and reward you with another spell to summon a bear to your side (Call Bear).

Notes
If you don't speak with Rolf Long-Tooth before you return the heart to Korst Wind-Eye, he never stops following you (until he dies). 
After completing this quest, you'll start seeing Horkers dying on all the northern shores of Solstheim.  This is related to the next quest.  Technically, they should be already dead, but the mechanics of the game do not allow for that.  So instead, you'll be treated to the sound of dozens of Horkers' dying moans every time you walk near the shores.  This will continue to happen every time you enter these areas from now on.
It is actually possible to start this quest at the same time as The Totem of Claw and Fang, however completing this quest first prevents you from getting the Summon Wolf spell.
This quest can also fail. This will happen if you do not start in time to finish it (encounter the Spirit Bear) by sunrise. If this happens, you will receive only the Summon Wolf spell. There is no opportunity to repeat this quest.

Bugs
 
Using the Console to set the quest stage to 25 may fix the problem.
 

Quest Stages