Bloodmoon:The Mead Hall Massacre

Quick Walkthrough
# During or after the Skaal test of Strength, enter the Meadhall of Thirsk, which should be destroyed.
# Talk to a survivor, Svenja Snow-Song, in Thirsk.
# (Optional) Loot anything you might want from the bodies, including the boots Paws of the Wolf-Runner.
# Find the beast's lair at the southeast corner of the Lake Fjalding.
# Slay Udyrfrykte and take the heart as proof.
# Give the heart to Svenja and hear about Hrothmund the Red, first chieftain of Thirsk.
# Travel to Hrothmund's Barrow and enter using the code word Ondjage.
# Activate the axe of Hrothmund in the barrow to receive his blessing.
# Return to Svenja for the sword Clanbringer, and to be hailed as the new chief of Thirsk mead hall.
# Bask in your glory, as described by Bereditte Jastal in Thirsk, a History.

Detailed Walkthrough
The Mead Hall is under Attack
During your travels, you may have heard of, or passed by the mead hall of Thirsk, just east of Lake Fjalding. During the Skaal test of Strength, if you enter for a quick drink, you'll find most of its patrons are dead. Speak with one survivor, Svenja Snow-Song, to find out that they were attacked by a terrible monster called Udyrfrykte, taking with it a severed leg of a patron. This mythical beast of some sort is rumored to make its home near Lake Fjalding.

Svenja pleads with you to take up the task of tracking and killing the monster. Be sure to loot anything you need (including a decent pair of magical boots called Paws of the Wolf-Runner), as the corpses disappear once the hall is repaired.
thumb|right|The Udyrfrykte

The Lair of the Monster
The beast's lair is nearby, west of Thirsk, at the southeast corner of the frozen lake. The lair is small and you'll find the creature at the end of it. The Udyrfrykte looks strange and rather frightening, almost like a big gorilla in a mask... ...almost. Its weapon is a Severed Nord Leg. It isn't as tough as some creatures you find during the main quest, but still more powerful that anything you'll find in the wilderness, so use caution as necessary. Be sure to loot the creature's heart as proof that you killed it (you can leave the severed Nord leg behind, unless you really want it). Be sure to check around the cave for a few trinkets, nothing special.

Return as the Hero of Thirsk
Return with the Heart of the Udyrfrykte to Svenja in Thirsk. You'll now find her outside the boarded up mead hall, closed since the Udyrfrykte killed nearly everyone. When you talk to her she'll take the heart automatically but there's one more task she wants you to perform. She asks you to find the barrow of Hrothmund the Red, first chieftain of Thirsk, and lay your hands upon his axe which lies therein. She mentions that while you're away she will start repairs on the hall. If you ask her for a little secret at this point, she will tell you that the name of the wolf that killed Hrothmund is "Ondjage". This is the password you will need to enter the barrow.

But wait, there is more
thumb|right|Hrothmund's Axe
Hrothmund's Barrow can be difficult to find if you don't 'get' the clue about it being in the eye of the wolf. You're looking for a group of large rocks that are shaped like a wolf, with the entrance in its eye. A complete description is given in The Patchwork Airship quest as the Barrow is involved there as well; you may also have acquired the barrow's password during that quest. Activate the axe in the barrow to receive a journal entry and a blessing.

Mead Hall Chief
When you return to Thirsk, the mead hall has been repaired and you are welcomed as the new chieftain. You can relax in your new quarters upstairs which includes a gift from Svenja, the magical Nordic long blade Clanbringer.

This is not the end of your business at Thirsk, one final glory remains. Speak to Bereditte Jastal upstairs to receive a new copy of Thirsk, a History, which now includes your exploits in becoming chieftain.

Notes
The quest becomes available while in the Skaal test of Strength, because that's when a fire pillar will appear on the lake, unsealing the Lair of the Udyrfrykte.
Refusing to help Svenja will cause her disposition to drop to 25. The quest won't end though and you can still talk to her again and accept.
The Udyrfrykte may be a reference to the beast Grendel in the epic Beowulf, which attacked the mead hall of Heorot, just like the Udyrfrykte attacks the mead hall in Thirsk. Further, the severed arm in Beowulf became the Severed Nord Leg here. Also, "Hrothmund" is a character in Beowulf, one of the sons of King Hrothgar.
If you cast Mark while inside Thirsk, then Recall into it after you have defeated the Udyrfrykye, there will be three workers inside who do nothing other than tell you to get out, as Thirsk is closed.
Be careful not to accidentally eat the heart, which counts as an alchemy ingredient, as this will prevent you from ever finishing the quest.
Hrothmund's blessing is random and can be Sanctuary (5 points) or Frost Shield (5 points) or both.

Quest Stages