Author's Note: This was written for this year's Het Big Bang challenge. This fic absolutely would not exist if not for my dearest Mem. Not only did she inspire me towards the premise int he first place, but she then did triple duty as my sounding board, my beta, and my indefatigable cheerleader. More than anything else, this Sif/Loki novel is for her.
This is based on the movie canon with a sprinkling of the myths and an even smaller dash of the comics. Mostly, I'm just making shit up. Of particular note, I took many liberties with the jotnar since in the film they don't really make any sense. Or to put it another way: they're built to be monsters, not to have a perceivably coherent, functioning society or culture. Which just so happens to be one of the main things I'm examining and deconstructing in this fic, thus it was important to make them... exist. So, as far as any glaring inconsistencies with regard to the jotnar presented in the movie: yeah, I know.
Not for the first time, Asgard went to war.
The Bifröst opened and the Æsir spilled out onto man's world so that the people of Midgard need no longer cower and shiver at the power of the Jötnar.
Heimdall stood on the bridge and watched. His post — Asgard's vanguard, their first defense — was more important even than the contributions he could make in battle. The forces of Asgard pushed and the Jötnar, outnumbered, fell back. They had made their way through the cosmos along Yggdrasill's limbs without the blessing of Odin Allfather. But their journey was difficult and unforgiving. It was unnatural for them to walk these paths; many fell along the way. Mortals still could not hope to challenge them, but Asgard ruled the Bifröst and through the Bifröst the Nine Realms. At the Allfather's word, at Heimdall's thought, the cosmos was open to the Æsir in all its vulnerability, open to accept their protection.
Laufey, king, resisted their routing as he always had their protection, as his father had before him, as his great grandmother had in the last war. Niflkist burned bright in his hands. He froze great swaths of Æsir like statues where they stood, but the terrible casket's true power was in Jötunheimr, was over Jötunheimr, and the Allfather was universal.
The Jötnar retreated, mankind supplicated, and the Æsir gave chase.
The Bifröst plucked them up, then set them down again, and Asgard spilled out once more, like searing sunlight betwixt curtains thrown back, onto the icy peaks and plains of Jötunheimr. Heimdall gazed, steady.
Odin sundered the gates of Utgarde and the Jötnar, still injured, scrambled before the force of Asgard. The men and women of ice — of cold hearts and cold blood — were brutal and vicious and never weak. Æsir blood colored the frost along with theirs as Odin marched through their fortress city, cut it open like a felled stag and rummaged for its heart.
In the temple at Utgarde's center, after all the guards had fallen, Odin came upon Niflkist and took it up. Jötunheimr wailed; its foundations cracked. Jötunheimr heaved around him.
In a corner, cocooned in furs, a child, tiny and soft, stirred but did not cry. Heimdall saw. Odin, less one eye — taken by Farbauti when Odin looked to slay her husband, before he left him dull and defeated instead — did not. Possibility flickered in the corner of Heimdall's eye, a path forked. Odin turned on his heel and walked away. Heimdall blinked; his vision cleared. He was no Norn to think of things that were not and would not be.
The armies of Asgard returned from crumbling Utgarde triumphant, the Bifröst lifting them away from the screech and snap of Jötunheimr shifting beneath their feet. Niflkist, styled the Casket of Ancient Winters, perched in a place of honor in Odin's vault, its glow dim, its power roiling. And at the last of the feasts, absent distraction, Odin at last presented his heir: a squalling babe in Frigg's arms, ruddy and golden in equal measures.
Asgard burned even brighter, rejoiced even more loudly in this new prosperity, and the voices of the Æsir filled the heavens.
In the distance, Jötunheimr quivered, creaked as if with deathly illness, and Heimdall turned his gaze away.