I’m going to expand upon all of this in a lengthier piece currently in-writing .. but here’s some brief notes pertaining to Hel (and a re-evaluation thereof) in a comparative Indo-European theological context. [The major issue that we have is how much weight to give various direct textual statements upon Hel and parentage / siblings thereof – although considering that these (mostly) appear to be Sturluson bits and pieces … there is, I think, reasonable ‘wiggle-room’ in some cases]
comparative Indo-European theology has, as a remarkably consistent element (if you know how to look) –
i) a ‘solar afterworld’ ;
ii) yes, a female deific playing one of the presiding roles over said afterworld / underworld conception.
So, for instance, in the Nordic sphere – Freyja & Folkvangr ; in the Vedic – Aditi ruling over the Pitrs ; and in the Classical, various points around Hekate & Persephone (but, then, I repeat myself – per various statements from the era upon the subject)
What appears to have occurred is a parallel ‘descent’ of afterworld into ‘underworld’ – what was once in the sky, across the sea (because the sky is also sea) , winds up ‘downward’ ; likely because .. well .. at night ..
Now, as for how this may pertain to Hel …
There is, again, a reasonably consistent typology for the relevant Mother Goddess to have both ‘light / dark’, ‘beautiful / terrifying’ , ‘living / dead’, ‘fair / black’ facings.
A good example for this is Parvati => Kali. Or, for that mat(t)er Demeter => Demeter Erinyes / Demeter Melaina (‘The Black’)
Now, while it’s a .. non-mainstream opinion, I suspect rather strongly that ‘Kali’ should have as an etymological root PIE *Kel – which is, surprise surprise, the particle that also informs “Hell”, “Hall”, etc. PIE *Kel meaning a ‘veil’ , ‘covering’, etc. – ostensibly also encompassing ‘veil between life and death’ [hence partially why Kaal etc. in Sanskrit winds up as ‘Night’, ‘Death’, ‘Time’]
In the Celtic sphere, we appear to see the figure of the Cailleach having the same ultimate linguistic origin. Because, once again, ‘Veiled One’.
I think – although I shall ahve to go back and check, that Demeter Erinyes’ description incorporates such a ‘Veiled’ reference ; certainly the notion of a black patina is in there -and with mythological / theological elements showing a fundamental consistency viz. Kali in other ways.
I have additionally pointed, in another sense, to the figure of Skadi as a ‘Shadow’-visaged (via the linguistics and comparative theology) Wife of Odin in just the similar manner. Certainly with commensurate responsibility around Sanctioning of the Unrighteous Dead (well, not that Loki was dead at that point …) via such serpentine means, and also for that matter having a prominent mythic arrangement of splitting time between one higher domain and one lower which recalls vaguely that of Persephone.
Where I am going with this is quite simple:
With Hel, it is possible that the linguistic coterminity may signify a greater degree of theological coterminity.
And, if so – then the typology we see elsewhere in the IE sphere around the Goddess in question having ‘Fair’ / ‘Black’ ‘facings’ that occur in sequential order … has evidently shifted somewhat for the Nordic iconographic expression for the deific in question – and instead these have become simultaneously co-occurrent.
It should also appear possible that some ‘confusion’ has eventuated as applies certain other prominent (indeed, ‘iconic’) associations of Hel – namely, that with a certain Wolf and that with a certain Serpent / Dragon.
By which I mean … while we have the post-Christianization accounting for Hel being related to a) Loki, b) Fenrir, c) Jormungandr … if the supposition that Hel has become in effect ‘demonized’ is correct then we might consider whether another Wolf is meant.
There is certainly a prominent attestation for Wolves in a metempsychotic context elsewhere for the Germanics (Valkyries riding thereupon), and other IE spheres similarly maintain associations for the relevant Afterworld Goddess in connection with such. Even before we consider whether The Wolf – the Sky Father in a lupine form – may be relevant.
A similar story may play out viz. the Serpent. Insofar as we encounter the Serpent in two ways in Indo-European mythology – the prominent role of the Adversary of the Gods (think Vritra, and yes Jormungandr) .. yet also we encounter Serpents as Punishers of those who would seek to violate the Cosmic Order (think of the Serpent utilized by Skadi to sanction Loki – or the prominent Serpentine associations of the Erinyes clade).
And this is before we get into the lesser-known Serpentine Forms of the Sky Father deific.
In short – it should seem not implausible that at some stage (whether by Sturluson’s hand or perhaps slightly earlier), somebody may have mixed up the connotations, the co-identifications of Wolves and Serpents and gotten the wrong figures involved.