Jotunheim was once the shadow used by Houses Aesir and Vanir to slaughter giants and keep their fighting skills up. In the aftermath of the collapse of both houses, one minor lordling of Aesir who survived saw his chance to build his own power base, using it.
Utgaard-Loki was a skillful enough shifter to be able to change his own mass, so he absorbed enough to become a giant and then went around whipping giants until he got them all to acknowledge him as King. He then turned them into a fighting force at his command and pledged fealty to King Dios, being made Lord Jotunheim.
House Jotunheim has a great hatred for House Wotan, which holds many of the survivors of its ancient foes.
"I trust him about as far as I can throw him."
While not a bad fighter, Utgaard-Loki is a thinker and trickster more than a warrior, preferring to fool his foes into self-destruction while he scampers away leaving them to die. At times, he seems to become intensely frustrated because most of his followers think 'Hulk Smash' is the epitome of careful plotting, however.
He is married to the equally sneaky Baba Yaga; they have a rather complex and messy, but sometimes incredibly productive, relationship.
Most of the house is made up of very big, strong, stupid warrior giants. However, the house has also attracted a handful of cunning exiles with enough shapeshifting to become giant-sized, who hold most of the leadership positions and provide the house with a leavening of sorcery and logrus.
Their children, rare now, appear to point the way to a union of the strength of the giants and the intellect of the Chaosians, and many expect the house will become very powerful in the centuries to come.
Jotunheim is a land of endless mountains with a long coast line riven by fjiords and river valleys. The giants roam over most of it, hunting and herding giant animals. There is a single city of note, Oslo, which is where Utgaard-Loki holds court.
Baba Yaga is a former Formorian and freak, known to kill and cook her enemies for later consumption. She is a cranky old woman, but is very smart, though she often hides it. She has a weakness for flattery, and is sometimes kind to small children, especialy if they call her grandmother.
She is a mage, conjuror, and logrus master of note and very strong too; she has a travelling hut which is rumored to contain an entire shadow on the inside, molded to her tastes. She also sometimes flies around in a huge iron bowl, carrying a giant pestle as a club. In fact, she seems to have an endless array of strange devices, knicknacks, and artifacts for every occasion.
She is married to Utgaard-Loki. It is a rather stormy relationship, but when they are getting along, it is extremely unwise to anger them.