Sigyn can found in the books Gylfaginning and Skáldskaparmál within the Prose Edda. In Gylfaginning, Sigyn is introduced in chapter 31 where she is the consort of Loki, they have a son called "Nari or Narfi". Sigyn is mentioned again in Gylfaginning in chapter 50, where events are described differently than in Lokasenna. Here, the gods have captured Loki and his two sons, who are stated as Váli, described as a son of Loki, and "Nari or Narfi", the latter earlier described as also a son of Sigyn. Váli is changed into a wolf by the gods, and rips apart his brother "Nari or Narfi".The guts of "Nari or Narfi" are then used to tie Loki to three stones, after which the guts turn to iron, and Skaði places a snake above Loki. Sigyn places herself beside him, where she holds out a bowl to catch the dripping venom. However, when the bowl becomes full she leaves to pour out the venom. As a result, Loki is again described as shaking so violently that the planet shakes, and this process repeats until he breaks free, setting Ragnarök into motion. Sigyn is introduced as a goddess, an ásynja, in the Prose Edda book Skáldskaparmál, where the gods are holding a grand feast for the visiting Ægir, and in kennings for Loki: "husband of Sigyn", "cargo [Loki] of incantation-fetter's [Sigyn's] arms", and in a passage quoted from the 9th-century Haustlöng, "the burden of Sigyn's arms".
The final mention of Sigyn in Skáldskaparmál is in the list of ásynjur in the appended Nafnaþulur section, chapter 75. Sigyn is a goddess of compassion and fidelity who remains one of the lesser known Norse goddesses during the heathen era. For those in need during troubled times of loss, Sigyn is a goddess of compassion and fidelity who remains one of the lesser known Norse goddesses during the heathen era. I am rather surprised by the lack of patronage to this Nordic deity (Loki's consort) but all those that do so will gain her help during times of bereavement or loss. She is a beautiful fidelity very loyal goddess and a boon to the family wellbeing especially during desperate hard times. I suspect though that because of the generalised filtered Christian mind-set in modern day Asatruers whowrongly identify Loki her consort as the Christian devil, the status quo regarding Sigyn will remain so sadly.