Signy is the only daughter of Volsung and Hljod and the twin sister of Sigmund.  She is betrothed to King Siggeir, with whom she has four sons, the first two murdered at her will by Sigmund because they were not tough enough to avenge her father’s death, the second at her will by Sinfjotli for betraying Sigmund and Sinfjotli. 

When Volsung gives her hand in marriage to Siggeir, Signy tells him that she will do as he wishes, but that she is wary of the marriage.  Volsung insists that she marry him.  For the wedding reception, Siggeir invites all of Signy’s family to come to his hall, where he plans to ambush her father and ten brothers.  Signy sends word to her family, but her father is killed anyway and her ten brothers are captured.  She begs for their lives, and instead of killing them outright, Siggeir ties them around the trunk of a very large tree where every night, a she-wolf comes to kill and eat one of them.  On the tenth day (only Sigmund is still alive), Signy sends a servant to spread honey all over Sigmund’s face and in his mouth.  When the she-wolf comes that night, she licks all of the honey off and when she puts her tongue inside Sigmund’s mouth, he bites it off and saves himself.

Signy helps Sigmund escape into the forest where he goes into hiding and begins planning how he will avenge his father’s death and kill Siggeir.  Signy helps him survive, and when she gives birth to each of her sons, she brings them to Sigmund to help him in avenging his father.  When Sigmund tells Signy that each of her sons are too weak and afraid, she demands that he kill them, and he does.

After the birth and subsequent death of her first two sons by Siggeir, Signy asks for the help of a sorceress who trades shapes with her.  Disguised as the beautiful sorceress, Signy goes into the forest where her brother Sigmund is hiding and “share[d] one bed with him” (Byock 43).  She became pregnant with Sinfjotli and when he is born, she takes him to Sigmund.  Sigmund finds Sinfjotli to be very strong and brave and raises him until he is old enough to kill Siggeir.

After some time, Sinfjotli and Sigmund come to Siggeir’s hall to kill him, but her two young children betray them.  Signy tells Sinfjotli to kill the children and he does without waivering.  Then King Siggeir captures them and buries them in a mound.  Signy throws Sigmund’s sword into the mound and they are able to escape, after which they set fire to Siggeir’s hall with him inside.  They ask Signy to come with them, but she refuses, saying to her brother: “Now you shall know whether I remember the slaying of King Volsung by King Siggeir.  I had our children killed when I thought them too slow in avenging our father, and I came to you in the forest in the shape of a sorceress, and Sinfjotli is our son.  Because of the he has so much zeal; he is the child of both a son and a daughter of the King Volsung.  In everything I have worked toward the killing of King Siggeir.  I have worked so hard to bring vengeance that I am by no means fit to live.  Willingly I shall now die with King Siggeir, although I married him reluctantly” (Byock 47).  Then she walked into the fire and died with her husband.