The myths and heroic poems are not wanting in ideal heroes, who are models of goodness of heart, justice, and the most sensitive nobleness. Such are, for example, the Asa-god Baldur, his counterpart among heroes, Helgi Hjörvarðsson, Beowulf, and, to a certain degree also, Sigurður Fáfnisbane.
Halfdan did not belong to this group. His part in the myth is to be the personal representative of the strife-age that came with him, of anage when the inhabitants of the earth are visited by the great winter and by dire misfortunes, when the demoralization of the world has begun along with disturbances in nature, and when the words already are applicable, "hart er í heimi" (hard is the world). Halfdan is guilty of the abduction of a woman - the old custom of taking a maid from her father by violence or cunning is illustrated in his saga.
It follows, however, that the myth at the same time embellished him with qualities which made him a worthy Germanic patriarch, and attractive to the hearers of the songs concerning him. These qualities are, besides the necessary strength and courage, the above-mentioned knowledge of runes, wherein he even surpasses his father (Rígsþula), great skaldic gifts (Saxo, Hist., Book 7), a liberality which makes him love to strew gold about him (Helg. Hund. I. 9), and an extraordinary, fascinating physical beauty - which is emphasized by Saxo (Hist., Book 1), and which is also evident from the fact that the Germanic myth makes him, as the Greek myth makes Achilleus, on one occasion don a woman's attire, and resemble a valkyrie in this guise (Helg. Hund. II.).
No doubt the myth also described him as the model of a faithful foster-brother in his relations to the silent Hamal, who externally was so like him that the one could easily be taken for the other (cp. Helg. Hund. II. 1, 6). In all cases, it is certain that the myth made the foster-brotherhood between Halfdan and Hamal the basis of the unfailing fidelity with which Hamal's descendants, the Amalians, cling to the son of Halfdan's favorite Hadding, and support his cause even amid the most difficult circumstances (see Nos. 42, 43). The abduction of a woman by Halfdan is founded in the physical interpretation of the myth, and can thus be justified. The wife he takes by force is the goddess of vegetation, Groa, and he does it because her husband Orvandil has made a compact with the powers of frost (see Nos. 33, 38, 108, 109).
There are indications that our ancestors believed the sword to be a later invention than the other kinds of weapons, and that it was from the beginning under a curse. The first and most important of all sword-smiths was, according to the myth, Thjazi4 , who accordingly is called faðir morna, the father of swords (Haustlöng 6 , Prose Edda Nafnaþulur 47). The best sword made by him is intended to make way for the destruction of the gods (see Nos. 33, 98, 101, 103). After various fortunes, it comes into the possession of Frey, but is of no service to Asgard. It is given to the parents of the giantess Gerd, and in Ragnarok it causes the death of Frey.
Halfdan had two swords, which his mother's father, for whom they were made, had buried in the earth, and his mother long kept the place of concealment secret from him. The first time he uses one of them he slays in a duel his noble half-brother Hildeger, fighting on the side of the Skilfings, without knowing who he is (cp. Saxo, Hist., Book 7, with Ásmund Kapp.). Cursed swords are mentioned several times in the sagas.
Halfdan's weapon, which he wields successfully in advantageous exploits, is, in fact, the club (Saxo, Hist., Book 1, Book 7). That the Germanic patriarch's favorite weapon is the club, not the sword; that the latter, later, in his hand, sheds the blood of a kinsman; and that he himself finally is slain by the sword forged by Thjazi, and that, too, in conflict with a son (the step-son Svipdag - see below), I regard as worthy of notice from the standpoint of the views cherished during some of the centuries of the Germanic heathendom in regard to the various age and sacredness of the different kinds of weapons.
That the sword also at length was looked upon as sacred is plain from the fact that it was adopted and used by the Aesir. In Ragnarök, Vidar is to avenge his father with a hjörr and pierce Fenrir's heart (Völuspá 54). Hjörr may, it is true, also mean a missile, but still it is probable that it, in Vidar's hand, means a sword.
The oldest and most sacred weapons were the spear, the hammer, the club, and the axe. The spear which, in the days of Tacitus, and much later, was the chief weapon both for foot-soldiers and cavalry in the Germanic armies, is wielded by the Asa-father himself, whose Gungnir was forged for him by Ivaldi's sons before the dreadful enmity between the gods and them had begun.
The hammer is Thor's most sacred weapon. Before Sindri forged one for him of iron (Gylfaginning), he wielded a hammer of stone. This is evident from the very name hamarr, a rock, a stone. The club is, as we have seen, the weapon of the Germanic patriarch, and is wielded side by side with Thor's hammer in the conflict with the powers of frost.
The battle-axe belonged to Njörd. This is evident from the metaphors found in the Prose Edda and in Íslendingadrápa 11.5 The mythological kernel in one metaphor is Njörðr klauf Herjan's hurðir, i.e., "Njörd cleaved Odin's gates" (when the Vanir conquered Asgard); in the other the battle-axe is called Gaut's meginhurðargalli, i.e., "the destroyer of Odin's great gate." The bow is a weapon employed by the Aesir Hödr and Ullr, but Baldur is slain by a shot from the bow, and the chief archer of the myth is, as we shall see, not an Aesir, but a brother of Thjazi. (Further discussion of the weapon myth will be found in No. 39).
Excerpt from: http://www.germanicmythology.com/ugm1/UGM1NEW20-43.pdf
Investigations into Germanic Mythology, Volume 1 by Viktor Rydberg