The name Sigar can refer to three people in Scandinavian mythology, surrounding the legends of Sigurd

Sigurd

Sigurd is a legendary hero of Norse mythology, as well as the central character in the Völsunga saga. The earliest extant representations for his legend come in pictorial form from seven runestones in Sweden and most notably the Ramsund carving Sigurd (Old Norse: Sigurðr) is a legendary hero of...

 the dragon slayer. One of them only appears as the friend of Helgi Hjörvarðsson in the eddic lay

Poetic Edda

The Poetic Edda is a collection of Old Norse poems primarily preserved in the Icelandic mediaeval manuscript Codex Regius. Along with Snorri Sturluson's Prose Edda, the Poetic Edda is the most important extant source on Norse mythology and Germanic heroic legends, and from the early 19th century...

 Helgakviða Hjörvarðssonar

Helgakviða Hjörvarðssonar

Helgakviða Hjörvarðssonar is a poem collected in the Poetic Edda, found in the Codex Regius manuscript where it follows Helgakviða Hundingsbana I and precedes Helgakviða Hundingsbana II...

. The other two appear as the villainous members of the same clan

Norse clans

The Scandinavian clan or ætt was a social group based on common descent or on the formal acceptance into the group at a þing.-History:...

 in several sources.

Icelandic sources

Snorri Sturluson

Snorri Sturluson

Snorri Sturluson was an Icelandic historian, poet, and politician. He was twice elected lawspeaker at the Icelandic parliament, the Althing...

 writes in the Skáldskaparmál

Skáldskaparmál

The second part of Snorri Sturluson's Prose Edda the Skáldskaparmál or "language of poetry" is effectively a dialogue between the Norse god of the sea, Ægir and Bragi, the god of poetry, in which both Norse mythology and discourse on the nature of poetry are intertwined...

that two Sigars belong to the same clan

Norse clans

The Scandinavian clan or ætt was a social group based on common descent or on the formal acceptance into the group at a þing.-History:...

, the Sikling

Sikling

The Siklings were a villainous clan in Norse mythology. In Skáldskaparmál, Snorri reports that they are descended from a Sigar who was the son of Halfdan the Old....

s, and that they are the relatives of Siggeir

Siggeir

Siggeir is the king of Gautland , in the Völsunga saga. In Skáldskaparmál he is given as a Sikling and a relative of Sigar who killed the hero Hagbard...

, the villainous Geatish king in the Völsunga saga

Volsunga saga

The Völsungasaga is a legendary saga, a late 13th century Icelandic prose rendition of the origin and decline of the Völsung clan . It is largely based on epic poetry...

.
In Hversu Noregr byggðist, it is given in more detail that Sigar the elder had two sons, Sigmund and Siggeir who killed Völsung

Volsung

In Norse mythology, Völsung was the son of Rerir and the eponymous ancestor of the ill-fortuned Völsung clan , including the greatest of Norse heroes, Sigurð...

. Sigmund had the son Sigar the younger, who killed Hagbard.

It is told in the Völsunga saga

Volsunga saga

The Völsungasaga is a legendary saga, a late 13th century Icelandic prose rendition of the origin and decline of the Völsung clan . It is largely based on epic poetry...

that Sigar the younger was in a feud with Hagbard

Hagbard

Hagbard , the brother of Haki and son of Hamund, was a famous Scandinavian sea-king in Norse mythology. He is mentioned in Skáldskaparmál, Ynglinga saga, Nafnaþulur, Völsunga saga and Gesta Danorum...

 and Haki

Haki

Hake, Haki or Haco, the brother of Hagbard, was a famous Scandinavian sea-king, in Norse mythology. He is mentioned in the 12th century Gesta Danorum, and in 13th-century sources including Ynglinga saga, Nafnaþulur, Völsunga saga...

 and his sons. He had kidnapped one of Haki's daughters and murdered a second:
Sigar the younger is also mentioned in Háleygjatal

Háleygjatal

Háleygjatal is a skaldic poem by Eyvindr skáldaspillir made in honour of Haakon Sigurdsson and his ancestors, in the end of the 10th century.The poem is only partially preserved in disjoint parts quoted in Skáldskaparmál, Heimskringla and two other manuscripts of kings' sagas. It appears to be a...

(as quoted in Ynglinga saga

Ynglinga saga

Ynglinga saga is a legendary saga, originally written in Old Norse by the Icelandic poet Snorri Sturluson about 1225. It was first translated into English and published in 1844....

), where a gallows is referred to as "Sigar's steed" (Sigars jó):

En Guðlaugr grimman tamdi við ofrkapp austrkonunga Sigars jó, er synir Yngva menglötuð við meið reiddu. Og náreiðr á nesi drúpir vingameiðr, þar er víkur deilir, þar er fjölkunnt um fylkis hreyr steini merkt, Straumeyjarnes.

By the fierce East-king Jorund Jorund or Jörundr was a Swedish king of the House of Yngling. He was the son of Yngvi, and he had reclaimed the throne of Sweden for his dynasty from Haki .Snorri Sturluson relates... s' cruel pride, Gudlog must on the wild horse ride -- The wildest horse you e'er did see: 'Tis Sigur's steed -- the gallows tree. At Stromones the tree did grow, Where Gudlog's corpse waves on the bough. A high stone stands on Stromo's heath, To tell the gallant hero's death.

Gesta Danorum

In Gesta Danorum

Gesta Danorum

Gesta Danorum is a patriotic work of Danish history, by the 12th century author Saxo Grammaticus . It is the most ambitious literary undertaking of medieval Denmark and is an essential source for the nation's early history...

(book 7), Saxo tells that Sigar had a daughter named Signy

Signy

Signy or Signe is the name of two heroines in two connected legends from Scandinavian mythology which were very popular in medieval Scandinavia. Both appear in the Völsunga saga, which was adapted into other works such as Wagner's Ring, including its famous opera The Valkyrie.The first Signe was...

. Sigar was in a feud with Haki's brother Hagbard

Hagbard

Hagbard , the brother of Haki and son of Hamund, was a famous Scandinavian sea-king in Norse mythology. He is mentioned in Skáldskaparmál, Ynglinga saga, Nafnaþulur, Völsunga saga and Gesta Danorum...

, but was informed by Signy's handmaid, that Hagbard had a secret love affair with Signy. Sigar decided to hang Hagbard, who, however, managed to inform Signy of this. Signy set her house on fire and succumbed in the flames while Hagbard executed himself in the gallows. Sigar tried in vain to save both Hagbard and Signy but failed. His only consolation was to bury the treacherous maid alive.

Gesta Danorum disagrees with the other sources by presenting Sigar as the son of Sywaldus, who was the son of Ungvinus

Yngwin

Yngwin was, according to Gesta Danorum, a king in Götaland, who was a close friend to one of the Danish kings named Halfdan.This Danish king had no sons, so he left his treasures and his kingdom to Yngwin...

, a Geatish king who became the king of Denmark.