A Game of ThronesEdit
Clement is sent by Ser Edmure Tully to the Golden Tooth with a Lord of House Vance from Wayfarer's Rest. Clement takes the troops sworn to House Piper with him and is tasked with guarding the pass against attacking forces of House Lannister. This happens at some point after Ser Gregor Clegane starts raiding in The Riverlands. Lords Piper and Vance are defeated at the Battle of the Golden Tooth, with Lord Vance killed in the fighting. Lord Piper manages to escape and is presumably at Riverrun when Robb Stark is declared King in the North.
A Feast for CrowsEdit
Lord Clement bends the knee to King Joffrey I Baratheon because his son, Marq, is held prisoner at the Twins after the Red Wedding. Lord piper is spared leniently, although Lewys is given as a squire to Ser Jaime Lannister.
Lord Clement is one of the riverlords who takes his troops to Riverrun to participate in the siege, as commanded by the Iron Throne. Whilst there he holds a lot of animosity towards House Frey due to their brutal murder of Robb, their continued imprisonment of Marq and the disappearance of numerous knights of House Piper who were cousins or nephews of Lord Clement. At the war council of Jaime Lannister he openly threatens Edwyn Frey, and is threatened in return by Ser Walder Rivers, leading to Lord Clement storming out.