 Valkyries are attested in the Poetic Edda , a book of poems compiled in the 13th century from earlier traditional sources ; the Prose Edda and Heimskringla ( by Snorri Sturluson ) , and Njáls saga , a Saga of Icelanders , all written in the 13th century . They appear throughout the poetry of skalds , in a 14th @-@ century charm , and in various runic inscriptions . 
