Aesir: The primary "pantheon" or group of Norse gods (led by Odin) - live in Asgard
Vanir: The secondary "pantheon" or group of Norse gods (led by Frey)
The two groups warred against each other early in time, but after that lived peacefully.
The Æsir were the guests of the Vanir: in Frey's palace the Dwellers in Asgard met and feasted in friendship. Odin and Tyr were there, Vidar and Vali, Njörd, Frey, Heimdall, and Bragi. The women were also there--Frigga, Freya, Iduna, Gerda, Skadi, Sif, and Nanna. Thor and Loki were not at the feast, for they had left Asgard together.
In Frey's palace the vessels were of shining gold; they, made light for the table and they moved of their own accord to serve those who were feasting. All was peace and friendship there until Loki entered the feast hall.
Frey, smiling a welcome, showed a bench to Loki. It was beside Bragi's and next to Freya's. Loki did not take the place; instead he shouted out, "Not beside Bragi will I sit; not beside Bragi, the most craven of all the Dwellers in Asgard."
Bragi sprang up at that affront, but his wife, the mild Iduna, quieted his anger. Freya turned to Loki and reproved him for speaking injurious words at a feast.
"Freya," said Loki, "why were you not so mild when Odur was with you? Would it not have been well to have been considerate of your husband instead of breaking faith with him for the sake of a necklace that you craved from the Giant women?"
Amazement fell on all at the bitterness that was in Loki's words. Tyr and Njörd stood up from their seats. But then the voice of Odin was heard and all was still for the words of the All-Father.
"Take the place beside Vidar, my silent son, O Loki," said Odin, "and let thy tongue which drips bitterness be silent."
"All the Æsir and the Vanir listen to thy words, O Odin, as if you were always wise and just," Loki said. "But must we forget that you brought war into the world when you threw your spear at the envoys of the Vanir? And you not permit me to work craftily on the Giant who built the wall around Asgard - tricking him to avoid his price?"
"You speak, O Odin, and all the Æsir and the Vanir listen to you! But was it not you who, thinking not of wisdom but of gold, brought the witch Gulveig out of the cave where she stayed with the Dwarf's treasure? You are not always wise nor always just, O Odin, and we at the table here need not listen to you as if you always were."
Then Skadi, the wife of Njörd, flung words at Loki. She spoke with all the fierceness of her Giant blood. "Why should we not rise up and chase from the hall this chattering crow?" she said.
"Skadi," said Loki, "remember that the ransom for your father's death has not yet been paid. You were glad to snatch a husband instead of justice. Remember who it was that killed your Giant father? It was I, Loki. And no apology has Odin asked me to give, although you have come amongst us in Asgard."
Then Loki fixed his eyes on Frey, the giver of the feast, and all knew that with bitter words he was about to assail him. But Tyr, the brave swordsman, rose up and said, "Not against Frey may you speak, O Loki. Frey is generous; he is the one amongst us who spares the vanquished and frees the captive."
"Cease speaking, Tyr," said Loki, dismissing him. "You might not always have a hand to hold that sword of yours. Remember in days to come what I have foretold."
"Frey," said he, "because you are the one giving the feast they think I will not speak the truth about you. But I am not to be silenced. Did you not send your messenger to Gymer's dwelling to bribe Gymer into allowing a marriage between you and his daughter, Gerda? Yes, Frey. For this marriage, you gave up the magic sword that you should have kept for the final battle, Ragnarok. You missed your sword when met the Giant, Beli, by the lake and nearly failed to defeat him and because you gave it up for your bride, all the realms are now in peril."
When he said this all who were there of the Vanir rose up, their faces threatening Loki.
"Sit still, ye Vanir," Loki railed. "If the Æsir are to bear the brunt of Jötunheim's and Muspelheim's war upon Asgard it was your part to be the first or the last on Vigard's plain. But already you have lost the battle for Asgard, for the weapon that was put into Frey's hands he bartered for Gerda the Giantess. Ha! Surtur shall triumph over you because of Frey's foolish bargain."
Then another appeared at the entrance of the feasting hall. It was Thor. With his hammer upon his shoulder, his gloves of iron on his hands, and his belt of prowess around him, he stood staring at Loki with wrathful eyes.
"Ha, Loki, betrayer," he shouted. "You planned to leave me dead in Gerriöd's house, but now thou will meet death by the stroke of this hammer."
His hands were raised to hurl Mjölnir. But the words that Odin spoke were heard. "Not in this hall may slaying be done, son Thor. Keep thy hands upon thy hammer."
Then shrinking from the wrath in the eyes of Thor, Loki ran from the feast hall. He went beyond the walls of Asgard and crossed Bifröst, the Rainbow Bridge. And he cursed Bifröst, and longed to see the day when the armies of Muspelheim, the Land of Fire, would break it down in their rush against Asgard, the realm of the Gods.
East of Midgard, the World of Men, there was a place more evil than any region in Jötunheim, the realm of Giants. It was Jarnvid, the Iron Wood. There dwelt witches who were the most foul of all witches. And they had a queen over them, a hag -- mother of many sons who took upon themselves the shapes of wolves. Two of her sons were Skoll and Hati, who pursued Sol, the Sun, and Mani, the Moon. She had a third son, who was Managarm, the wolf who was to be filled with the lifeblood of men, who was to swallow up the Moon, and stain the heavens and earth with blood.
To Jarnvid, the Iron Wood, Loki made his way. And he wed one of the witches there, Angerboda, and they had children that took on dread shapes. Loki's offspring were the most terrible of the foes that were to come against the Æsir and the Vanir in the time that was called the Twilight of the Gods.