House Thorvald was a Great House during the time of the later Corrino Empire, and was based on the planet Ipyr.
During the time of Emperor Shaddam Corrino IV, the House was headed by Earl Memnon Thorvald, who as leader, married his sister, Firenza Thorvald to Shaddam Corrino IV in 10,187 AG. Firenza was unable to bear Shaddam any royal heirs in addition to the five daughters that he already had, and in a few years, Firenza fell out of favor with him. She died within one or two years of her marriage to the Emperor, leaving Memnon somewhat embittered.
During the Ascension of House Atreides a few years later, Memnon took upon himself the dangerous position of being the leader of the rebellion against the new Emperor, Paul Muad'Dib. When Paul gave his first speech before the Landsraad in 10,194 AG after the jihadi sacking of Kaitain, Memnon walked out of the speech after defiantly yelling at Paul, saying that he'd "had enough of Emperors!"
Soon afterwards, Memnon organized Houses that were in rebellion to Paul under the leadership of House Thorvald. They put up a guarded defense of Galicia a few years later, against the forces of Gurney Halleck in 10,196 AG; although the Emperor's forces eventually won. After the first assassination attempt on Paul's life in 10,198 AG at the Great Surrender Ceremony on Arrakis, House Thorvald initially claimed to have orchestrated the complex plot, though it was found out to be Whitmore Bludd.
Later that year, Paul discovered through prescience that Memnon and his allies were planning to attack and destroy Caladan, and kidnap or kill Paul's mother, Jessica. Paul immediately summoned the Guild representative Olar, who took him to the Navigator Beric. It was confirmed that House Thorvald had indeed conspired to destroy Paul's homeworld, and that fighter starships were in heighliners waiting to be transported to the water-world.
Paul ordered that all of the House Thorvald ships, as well as all of Thorvald's allies be stranded in deep space, without any provisions. He further commanded that House Thorvald be eliminated, and their homeworld of Ipyr be sterilized, and House Thorvald ceased to exist.
Sources: Heroes of Dune?,