Those who hear the fairy tales of Swan Maidens might get the mistaken idea that these are weak damsels, this, however, is not the case. Fairy tales are often about people besting forces greater than themselves, within them peasants and fools defeat dragons and giants and young men can kidnap a powerful being to be their wife.
The Swan Maiden is related to Valkyries, they may also be related in some way to the fates which control the fate of humanity. In the Hromundarsaga 'Kara,' who the
Edda says was a second born of Svava, appears as an enchantress in a
swan shift and hovers above the hero Helgi singing. By her assistance Helgi
had always found victory but it happened in one fight that he swung his
sword too high in the air and hewed off his lovers food, she fell to
the ground and his luck was spent.
Like many fairy beings it may be of course that Swan Maidens are capable of granting great strength which they don't possess. Such a motif is common from Europe to Japan. In one Japanese tale for example a farmer threatens to strike down a Thunder Kami who doesn't promise to give his child Herculean strength. So we see humans are more susceptible to fairy magic than fairies are.
Fairy tale with a Swan Maiden