Jormuttar is Soo Fat... requires friendly with The Sons of Hodir. It is a side quest in the overarching Sons of Hodir quest chain.
King Jokkum in Dun Niffelem wants you to slay Jormuttar in Hibernal Cavern.
I have an opportunity that will help you to gain approval with my people, provided you prevail.
The jormungar are a nuisance best dealt with quickly. If given any quarter, they breed like hares and spread like fire.
They have appeared southwest of here, in the Hibernal Cavern. If their spawnmother is not slain soon, they will gain a foothold in our region.
She cannot refuse food. Take this knife and get the flank of a bear corpse from their cave. Place it near her crater and kill her as she feeds.
Have you slain Jormuttar?
So it is done.
We have heard the screams of Jormuttar as they echoed from across the valley.
You have done our people a service this day, little <race>.
It will take a few tries using the skinning knife to get an appropriate bear. Also, sometimes this quest must be completed before King Jokkum will help you complete Krolmir, Hammer of Storms
The quest name is likely a reference to the popular "Yo Mama is so fat..." jokes.
-  They Took Our Men!
-  Leave No Goblin Behind
-  The Crone's Bargain
-  Mildred the Cruel
-  Discipline
-  Examples to be Made
-  A Certain Prisoner
-  A Change of Scenery
-  Is That Your Goblin?
-  The Hyldsmeet
-  Taking on All Challengers
-  You'll Need a Bear
-  Going Bearback
-  Cold Hearted
-  Deemed Worthy
-  Making a Harness
-  The Last of Her Kind
-  The Warm-Up
-  Into the Pit
-  Prepare for Glory
-  Lok'lira's Parting Gift
-  The Drakkensryd
-  Sibling Rivalry
-  Mending Fences (+28,600 The Sons of Hodir)
-  The Refiner's Fire
-  A Spark of Hope (+28,600 The Sons of Hodir)
-  Forging an Alliance (+325 The Sons of Hodir)
Mandatory side quest:
-  You Can't Miss Him (+97 The Sons of Hodir)
-  Battling the Elements (+98 The Sons of Hodir)
- Prerequisite for daily: [80 Daily] Hot and Cold (+455 The Sons of Hodir)
-  A New Beginning
-  Veranus
-  Territorial Trespass
-  Krolmir, Hammer of Storms (+455 The Sons of Hodir)
Mandatory side quest:
-  Jormuttar is Soo Fat... (+325 The Sons of Hodir)
-  In Memoriam (+325 The Sons of Hodir)
-  A Monument to the Fallen (+97 The Sons of Hodir)
-  The Terrace of the Makers
-  The Earthen Oath &  Loken's Lackeys
-  The Reckoning
- [80D] Whatever it Takes! (+650 The Sons of Hodir) & [80D] Diametrically Opposed