In Norse mythology, Sigyn is Loki, the trickster god's wife.
Very little is known about her, and she's referred to only in a
handful of paragraphs.
According to the stories, Sigyn is loyal to her husband even
after his punishment for the death of Balder, where he was
chained between some large boulders and a poisonous snake was
placed over his head. Sigyn
stays beside him holding a bowl over
him to catch the poison. When the bowl is full, however, she
has to leave his side to go empty it. When the poison drips in
Loki's face he writhes in pain, causing the Earth to tremble.
Sigyn is sometimes referred to as Sygin or Syngin.
In the Elder Edda, Sigyn apprears in the following
paragraphs, the first taken from Volsupa:
"She saw a captive lying under the grove of hot springs,
That evil-loving form, Loki she recognised;
There sits Sigyn, not at all happy
about her husband - do you understand yet, or what more?"
..and in Lokasenna
"He (Loki) was bound with the guts of his son Nari. But his
son Narfi changed into a wolf. Skadi took a poisonous snake and
fastened it over Loki's face; poison dripped down from it.
Loki's wife, sat there and held a basin under the poison. But
when the basin was full, she carried the poison out... "
..and in a longer passage in the Gylfaginning
"Then Loki's sons Vali and Nari or Narfi were fetched.
turned Vali into a wolf and he tore his brother Narfi to pieces.
Then the Aesir took his guts and bound Loki with them across the
three stones - one under his shoulders, one under his loins, the
third under the backs of his knees - and these bonds turned to
iron. Then Skadi got a poisonous snake and fixed it up over him
so that the poison would drip from the snake into his face. But
his wife Sigyn stands next to him
holding a basin under the drops
of poison. And when the basin is full
she goes and pours away the
Sources: Various, most notably http://loki.ragnarokr.com/
Translations from the Elder Edda by Larrington
Translations from the Younger Edda by Faulkes