Odin’s son, Vidar appears in Eddic poetry in Voluspa 55, Vafthrudnismal 51 and 53, Grimnismal 17 and Lokasenna 10.

His main purpose is to avenge his father’s death. Grimnismal 17 provides us a glimpse of the scene. In his vision of the dwellings of the gods in Grimnismal, Odin describes Vidar's "land" last, in stanza 17, and says it is grown with brushwood and tall grass:
 

This harks back to the same half-line quoted in Havamal 119:

Then Thor proceeded to the river named Vimur, greatest of all rivers. There he girded himself with the Girdle of Might and braced firmly downstream with Gridr's Rod, and Loki held on behind by the Girdle of Might. When Thor came to mid-current, the river waxed so greatly that it broke high upon his shoulders. Then Thor sang this:

Wax thou not now, Vimur,
For I fain would wade thee
Into the Giants' garth:
Know thou, if thou waxest,
Then waxeth God-strength in me
As high up as the heaven.

Then Thor saw Gjálp, daughter of Geirrödr, standing in certain ravines, one leg in each , spanning the river, and she was causing the spate. Then Thor snatched up a great stone out of the river and cast it at her, saying these words: 'At its source should a river be stemmed.' Nor did he miss that at which he threw. In that moment he came to the shore and took hold of a rowan-clump, and so climbed out of the river; whence comes the saying that rowan is Thor's deliverance.

Now when Thor came before Geirrödr, the companions were shown first into the goat-fold for their entertainment, and there was one chair there for a seat, and Thor sat there. Then he became aware that the chair moved under him up toward the roof: he thrust Grídr's rod up against the rafters and pushed back hard against the chair. Then there was a great crash, and screaming followed. Under the chair had been Geirrödr's daughters, Gjálp and Greip; and he had broken both their backs. Then Geirrödr had Thor called in the hall to play games. There were great fires the whole length of the hall. When Thor came up over against Geirrödr, then Geirrödr took up a glowing bar of iron with the tongs and cast it at Thor. Thor caught with his iron gloves and raised the bar in the air, but Geirrödr leapt behind an iron pillar to save himself. Thor lifted up the bar and threw it, and it passed through the wall, and so on out, even into the earth. Eilífr Gudrúnarson has wrought verses on this story, in Thórsdrápa.

Þórsdrápa 9:5-8 at The Jörmungrund site:

9/6: völ Gríðar = Gríðarvöl. There is no evidence for such a staff outside Snorri's prose account of the tale. This account is extremely dubious (see Analogues). We have already learned that Thor withstood the force of the ocean currents by plunging his spear into the bottom of the ocean. He must surely have used both hands to do so. So how can he suddenly be wielding this so-called Gríðarvölr "staff of Gríðr"? It is clearly absurd. Gríðr was a giantess, the mother of Víðarr by Óðinn. Snorri's tale seems to be made out of whole cloth, or perhaps his failed attempts to understand the complex language of Þórsdrápa.