Everything the medieval sources say about Angrboða can be written out in full in under a hundred words, and it is worth doing so before anything else, because almost nothing you will read about her elsewhere comes from them.
Gylfaginning, chapter 34: Loki had three children by a giantess in Jötunheimr called Angrboða — the wolf Fenrir, the serpent Jörmungandr, and Hel. The gods learned by prophecy that great harm would come from these siblings, and Alföðr had them fetched to him.
Hyndluljóð, stanza 40: Loki begot the wolf on Angrboða.
Völuspá hin skamma, quoted within Hyndluljóð, refers to the same.
That is the corpus. She has no dwelling described, no appearance, no speech, no genealogy, no death and no further appearance.
A name that is a job description
Angrboða means "the one who brings grief" or "sorrow-bringer" — angr, grief or trouble, plus a noun of announcing or bidding, from the same root as English bode.
That is a description of her narrative function rather than a personal name, and it is worth taking seriously as a possibility: the sources may not be naming a figure so much as labelling the mother of three disasters. Norse tradition does this repeatedly — Höðr means slaughter, Váli's name may mean "of the slain," Þökk means thanks.
An Angrboða is also named once in Völuspá's giant-lists as a giantess in Járnviðr, the Iron Wood, and Snorri says an old giantess in Járnviðr breeds the wolves who chase the sun and moon and produces Mánagarmr. Whether that is the same figure is not stated. If it is, she is the mother of every wolf in Norse eschatology.
Why the gaps matter
Angrboða is the clearest single case of something that runs through the whole tradition: the sources preserve women in mythology at a fraction of the resolution they preserve men. She is the mother of the three beings who between them kill Odin, kill Thor and hold the dead — and she gets one clause, twice.
Compare the treatment of her children's father, who has entire poems. The asymmetry is not because she is minor; it is because the surviving corpus was written down by men, largely for aristocratic male audiences, and preserved what those audiences wanted repeated.
An empty space that contemporary fiction has rushed to fill
Because the space is empty, it has been filled. She has become one of the most reinvented figures in contemporary Norse-derived fiction.
God of War Ragnarök (2022) gives her the largest role she has ever had: a young giantess, the last of the Jötnar of Jotunheim, with prophetic abilities, a home in Ironwood, a relationship with Atreus, and a complex position between the giants and the gods. Neil Gaiman, Joanne Harris's The Gospel of Loki and a considerable body of published and unpublished fiction have taken her up as a witch, a wolf-mother, a rival to Sigyn, or a sympathetic partner destroyed by the Æsir. Modern heathen practice has in places adopted her as a figure of wildness and of mothers whose children are taken.
None of that is in the sources, and none of it is illegitimate — retelling is what mythology is for. But there is a difference between an author's Angrboða and a medieval one, and the difference has been blurred so thoroughly online that summaries of "Norse mythology" now routinely attribute the God of War biography to the Eddas.
A specific example: the widely repeated claim that Angrboða was burned three times by the Æsir and revived each time, and that her heart was eaten by Loki, is a conflation. Hyndluljóð describes Loki eating a half-cooked woman's heart found in the embers and becoming pregnant from it, and separately mentions a woman called Heiðr or Gullveig who was burned three times and reborn in Völuspá. The poems do not identify either woman as Angrboða. Later readers joined them.
The one thing she demonstrates
Angrboða's children are the whole engine of Ragnarök. The gods' response to each of them — bind the wolf, throw the serpent into the sea, give the daughter the dead — is a set of preventive measures, and each measure is precisely what makes the prophecy come true. The wolf is dangerous because it was bound and betrayed; the serpent encircles the world because it was thrown into the sea and grew there.
The mother is the point of origin for that entire mechanism and never appears in it. See the Norse family tree for how her line runs through the mythology, and the Norse overview for the limits of what the sources preserve.
Is Angrboða the same as the witch Gullveig or Heiðr?
There is no textual basis for the identification and a good deal of momentum behind it. Völuspá describes Gullveig, pierced with spears and burned three times in Hár's hall and reborn each time, and says that when she came to a house she was called Heiðr, a seeress skilled in magic and welcomed by wicked women. The poem does not connect her to Loki, to Jötunheimr or to any children. The link to Angrboða is a modern synthesis, sometimes attributed to nineteenth-century scholarship, and it should be labelled as interpretation rather than reported as content.
Why does Snorri call her a giantess when Loki is one too?
Loki's own status is the more unstable of the two. He is the son of the giant Fárbauti and Laufey, counted among the Æsir, and Odin's sworn blood-brother — which makes him a jötunn by descent and an Ás by association. Angrboða is simply placed in Jötunheimr with no ambiguity at all. The pairing is therefore not a mixed marriage in the way it is often described; it is a giant fathering giant children on a giant, and the anomaly is that one of the parents was living in Ásgarðr at the time.