Dag the Wise or Dagr spaki was a mythological Swedish king of the House of Ynglings (dated to the 4th century by 16th-century historiographer Johannes Magnus).
When the bird was killed on one of these trips, Dag invaded Reidgotaland (considering the date and location, apparently Gothiscandza), in order to avenge it.
The earliest two versions based on Ynglingatal, i.e. Historia Norwegiæ and Íslendingabók (see below) say that Dag was succeeded by his sons Alrekr and Eírikr who in their turn were succeeded by Dag's grandson Agne (in Historia Norwegiæ incorrectly called Hogne[1]): Historia Norwegiæ: Cui [Dyggui] successit in regnum filius ejus Dagr, quem Dani in quodam vado, quod Sciotanvath vel Wapnavath dicitur, dum passeris injurias vindicare conaretur, publico bello occiderunt.
Alricr autem genuit Hogna[2] His [Dyggve's] son Dag succeeded to his throne; he was killed by the Danes in a royal battle at a ford named Skjotansvad, while he was trying to avenge the violence done to a sparrow.
En er þeir fóru yfir á nökkura, þar sem heitir Skjótansvað eða Vápnavað, þá rann fram ór skógi einn verkþræll á árbakkann ok skaut heytjúgu í lið þeirra, ok kom í höfuð konungi skotit; féll hann þegar af hestinum ok fékk bana.
Í þann tíma var sá höfðingi gramr kallaðr er herjaði, en hermennirnir gramir.
As they were going across a river at a place called Skjotan's [the Weapon's] Ford, a labouring thrall came running to the river-side, and threw a hay- fork into their troop.