The son and heir of Brytta Léofa. During his father's reign, Rohan had suffered warfare with Orcs that had descended from the North, and attempted to settle in the White Mountains. The were driven out, and by the time Walda came to the throne, it was thought that the land was free of Orcs. In the ninth year of his reign, however, Walda was slain by them near Dunharrow. He was succeeded by his son Folca, who avenged his father's death.
There is some confusion over the date of Walda's death. The list of Kings of the Mark in Appendix A to The Lord of the Rings records that he was slain in III 2851, but the Tale of Years entry for III 2800-64 states 'Orcs from the North trouble Rohan. King Walda is slain by them (2861)'. Given what we know of Walda's biography (specifically that he ruled for just nine years after succeeding his father Brytta in III 2842) the former date of III 2851 must be the correct one. The '2861' in the Tale of Years therefore appears to be a simple typographical error, but it persists even in the latest editions of The Lord of the Rings.