Familiarity with Norse myth

Is it asking too much to expect this snippet to be enough to explain why a character named Hel is crippled? Or is this enough for most people?

Well, it clearly explains that she IS crippled, and named after a mythical character crippled the same way. I'm not sure it explains WHY she's crippled, if there is supposed to be a particular reason beyond an unfortunate trick of biology or something. Of course, from just this excerpt out of context I don't know if this is the actual Hel of myth, or just someone named after her.
Somebody who doesn't know Norse mythology still wouldn't know this is a reference to that just from your excerpt, though, since you specifically avoided saying what mythology she's from. "An old Viking legend" could work for that instead of "a Northern European legend" perhaps, still without feeling like you're beating the reader over the head with it.

It doesn't really explain why she's crippled, but it certainly beats you about the head and shoulders with the reason she's named Hel. And it seems a bit forced to me, but that could be due to it being excised from its natural context.

that's comforting, someone commented that I was expecting too much from the reader to make the connection since apparently almost no one knows Norse myth and had to have this section pointed out to them to note I'd explained somewhat

granted, he's from the pre-reader set that don't normally read sci-fi fantasy....

If you know that specific variant, then it's pretty clear. The thing is, the people who know that variant of the Norse myth won't need as much discussion about it as you have.

Of course, there are multiple versions of Hel, as mythology is rarely as clean and consistant as modern mythological compilers tend to present it. The Norwegian, Icelandic, Danish, and Scandinavian versions of these myths vary wildly from each other, as much as their languages do.

You don't need Norse mythology for that. The parents named her Hel because of a deformity (definitely not a good-parent thing to do), so unless they waited until later in life to give her a name, presumably she was born with it.

good, that's about where I want it to be....

just got taken aback by the "you never really explain why she's so injured" comment and realizing it was being said about Hel.

especially since the word I use the whole story for her is "crippled"

Either way i think the information is given clearly enough to understand the back story and interesting enough to progress it. Not that you asked for criticism right out...Also out of curiosity did you write this or is it written by someone else?