Death is a part of life, he is told later, even in the Realm Eternal. No one explains why, and he still doesn't know how to ask. Eventually he accepts it, because death is in fact an inescapable part of life, especially for a culture of warriors, but accepting reality does not mean he truly understands. It only means he stops trying to understand.
Lifetimes away from that child exploring the city streets, he hangs from the wreck of the shattered Bifrost, unable to think of a single reason for holding on, and so he opens his hand, and falls, and expects to die.
He doesn't.
Thanos and his lackeys teach him what it means to long for death, but that is not understanding either, only pain and despair.
Frigga is not dead. She cannot be dead because there is no body (he has seen no body) and no funeral (he is not allowed to attend her funeral and no one will tell him any details until long after, when he is wearing another face). She is not dead because she cannot, cannot be dead—
He wakes cold and alone on Svartalfheim. Thor's cry of grief still rings in his ears, but Thor himself is nowhere to be found. He had to do something about Malekith and the Convergence, of course, could not be Thor and simply stand by to grieve over his brother's empty corpse, but for a moment Loki wishes, foolishly—
Well, it has never mattered what Loki wishes, has it?
For the first time in a very long time—certainly decades, probably centuries—he thinks of the cat again, how limp it was on the stone pavement, how utterly, unnaturally still. How Thor was so certain it was dead, and he wonders now if Thor was wrong about that too, if they left it behind to die alone.
He never does see Frigga's body, even later, because she was given to the stars while he stayed buried and suffocating underground. There is a memorial, and he orders another one, but it all seems hollow and unreal. Instead there is only a great absence, and no statue or painting, no matter how beautiful or lifelike, can fill it or change it.
She deserves a better memorial than lifeless stone, he thinks eventually. There is a species of tree, native to Vanaheim but extinct there for millennia; it is tall and graceful, at least in pictures, with silver bark and golden leaves, and he fixates on it, knowing it won't bring her back but unable to shake the idea that it might mean something. Other things demand his attention, more important things, and for weeks at a time he ignores them entirely, first searching the Realms for a seed and then, when at last he finds one (desiccated but perfectly preserved in a long-forgotten Jotun tomb, of all places, and the irony is not lost on him, even as he takes care to disturb nothing else), coaxing it into life.
The day the seed finally sprouts, he is sitting in the rooms that used to be Frigga's, wearing his own face because the doors are warded and it is exhausting always existing within the guise of someone else. There is still so much he needs to do, the mundane duties of rule and the looming specter of the Titan, but he is tired and entirely alone and it is so hard, sometimes, to remember that there is a point to any of this. Gradually he realizes that he is thinking, rather absurdly, of the cat again, as he watches dust motes drift through a shaft of sunlight—the cat and how it was alive and then it wasn't, and how death has never quite lost that sense of wrongness, no matter how many times he has experienced it since. More than anything else, it is a fundamental wrongness in the universe, that he is still here and Frigga is not.
A flash of color in the pot catches his eye. He stands—slowly, stiffly, as if he's as old in truth as his now-customary glamor makes him look—and crosses the room to the window, where he placed the pot to catch enough sunlight. A tiny, pale curl of green is sticking up out of the soil. It looks almost impossibly fragile, and easy to crush, but it is already reaching toward the light.
Loki stands there for long time, just looking at the seedling and feeling the sunlight on his hands. He has the brief, absurd thought that perhaps Frigga and that long-dead nameless cat will find each other in Valhalla. It's a fanciful notion, a child's thought, but the aching child inside him takes a little comfort from it, if only for a moment.
Additional notes:
This odd, sad little fic exists purely because of the original scene with the cat. That part happened to me, more or less, and I didn't really know how to process it, so the obvious thing was to put Loki in the same situation so he could...also not deal with it. It wasn't quite the same for me, of course: this happened recently, so I was 30, not a kid, and of course it was a car, not anything involving a horse. I responded better than Loki does here, too. (I don't know exactly why I want to tell this story after having just retold it through fic, but I do, so: I was on vacation in Dublin and walking to a bus stop in a residential area with my friend, and we saw that traffic had stopped and then saw the cat; I froze at first too, like the other shocked people standing around who'd come out of their houses. Then I heard the asshole driver saying the best thing would probably be to run it over again to put it out of its misery, and that got me moving; I carried it out of the road to the sidewalk-asshole driver immediately left, having never even gotten out of his car-and took off its collar looking for ID. A woman who lived nearby stayed but didn't know what to do, so I took charge a little bit, seeing she had a smartphone and telling her I didn't have data outside the US so she needed to Google an emergency vet and call them so they could help. Another woman let me into her house to wash off the blood. And then my friend and I left to catch our bus, because at that point there wasn't anything else we could do. I should also note that everything with Thor is fabricated purely for this story and has nothing to do with my friend, who was also upset.) But the rest is...more or less exactly what happened, at least the incident itself, the details about the cat, and how it all felt, and it stuck with me, the way it sticks with Loki here.
I don't understand death either, is the thing. I've never lost a close friend or relative (although I realize it's just a matter of time), so I've never really been forced to deal with it. At most it's been something peripheral to me, close enough to feel wrong and surreal but not close enough to be awful and personal. My own cat had to be put down, several years ago, and that was surreal in a bad way too, but I still had my dog, and a new cat came into our lives shortly after, so it was...different. A few days after the Las Vegas shooting, I learned that one of the victims was a good friend of my sister and brother-in-law; I never met him so it's still not personal for me, but even for me it feels wrong to suddenly have this violence come closer to home and even closer to my sister (who's gone out of state for country concerts before and could easily have been at this one, if she didn't have a baby to take care of). Even at a remove from me, or when it's something like that cat in Dublin where it's physically close but not anyone I know, I just sort of...can't make sense of it, that a living being was alive and part of others' lives and just isn't anymore. None of that's unique to me, I know, and I doubt this fic has done anything to make it make any more sense to me or anyone else, but...I guess I wanted to write and share it anyway.
Oh, and in case anyone's curious: when I said that this was originally going to be sadder, I meant that it wasn't going to have the whole final bit about the seed (in other words, it would have ended with the previous section about Svartalfheim), because I didn't think of that until later. But then I did think of it and basically went "oh thank God, I can end it on a note that isn't completely crushing."