Salomon was the son of Riwallon III of Poher. In 851, Charles the Bald, after his defeat at the Battle of Jengland, made peace with Erispoe, the Breton duke, and granted him the counties of Rennes and Nantes and the Pays de Retz in Poitou as far as the river Mayenne. In 852, Salomon swore an oath to Charles and became his loyal follower ("fidelis"); in return, in a manner similar to Erispoe, he was granted Rennes, Nantes, and Retz as a "third" of Brittany to be held from Charles in fee. He and Erispoe were the "dominatores" of Rennes in 853. Salomon was the most powerful aristocrat at Erispoe's court.