Loki has had various children, sometimes as a mother, sometimes as a father. One brood in particular is important.
Odin took these children from their parents (Loki and Angrboða) and banished each to a different place in a different realm.
Fenrir, the great wolf, they raised themselves, but, fearing him, they bound him, acting as if it were a game. Twice they did this and he escaped. The third time they used a special magical rope, promised they would free him if he could not free himself (they lied) and this time he did not escape. Initially on good terms with the gods of Asgard he ended up understandably pissed off. When the world ends it is foretold that he will kill Odin.
Jörmungandr, the great serpent, was cast into the oceans of Midgard (earth.) He grew so large that he wrapped around the world and now grasps his own tail in his mouth. It is said that when he lets go the world will end. I can't find the source for the whole "When he lets go the world will end" thing, so I don't have the details, but I've always had the impression that the world has become, or has always been, unstable such that if too much time passed without Jörmungandr coiled around it, holding it together, it will simply fall apart. Thor doesn't like Jörmungandr very much, and the two are fated to kill each other.
The third child from this brood was Hel.
She is the only daughter of Loki whose name we know. Perhaps the only divine daughter of Loki. Perhaps the only daughter of Loki period.
When Hel was born she already had the form of an old woman. Odin cast her into the afterlife, but, unlike the others, he put her to work. Hel is a ruler. The place she rules is named after her (it is called Hel or Helheim.) With with exceptions (looking at you Valhalla), the dead go there. Even dead gods. We'll get back to that.
Those that die of sickness or old age are sent there automatically. Some of those that die in violence do as well. That much is crystal clear. What's cloudy bordering on opaque is exactly how the determination is made. Obviously having your soul snatched by Odin or a Valkyrie is a get out of Hel free card, but is that the only way? Not clear.
Baldr goes there when he dies.
Now the question of what Baldr does when he gets there is not even remotely close to being answered. When Hel got there she set up a queendom and got the place named after her. Of course she was under orders. Like I said, Odin put her to work. She was ordered by his high and mightiness to receive all that came to her and thus she had to create some kind of civilization with which to greet the dead. (Presumably by, at least in part, organizing those dead who were there already.)
Baldr shows up and does ... what exactly?
So I was thinking about this, and talking it out with Lonespark, and it occurred to me that Baldr being in Hel's embrace for all this time might not be an accident.
Persephone and Hades eventually worked things out and Hades fucking kidnapped her.
Think about the whole story: A self fulfilling prophesy, wheels greased by Loki, sends the universe's most eligible bachelor to live with his daughter for eternity.
Does this sound like, "Fate sucks," or does it sound more like, "Dad, I've been dating someone and we really want to be together forever but the political ramifications of openly marrying could shake Yggdrasill to its foundations. Plus, it's kind of hard for him to keep sneaking here unnoticed, it would be better if we could find some kind of reason for him to relocate here without letting people know why. Can you help?" as said by Hel to Loki?
Doesn't the second one make more sense? You can see how it goes from there. Loki says he'll think about it then tells Baldr to start complaining about nightmares of dying.
One mistletoe spear later and Hel and Baldr are living happily together. Sure, it'll bring about the end of the universe as we know it, but everything's gotta end sooner or later, right?
Since Lonespark and I talked about it she's pointed various things (including, most recently, a poem) my way by people who came to similar conclusions.