On his 21st year, his father put him in charge of the family's sheet diamond mines on Hagal. Piers however was against his family's cutthroat policy. He respected the slaves (called them 'workers') and insisted they deserved rights, and let them work without typical Harkonnen regulations and close oversight; something that would augment their productivity and benefit his own family.
Ulf wasn't impressed when he discovered this and took him to Salusa Secundus. During the trip however, their family yaught was attacked by Agamemnon and other 6 cymek ships. When all hope was lost, Piers was secured in a lifepod but it was too late for his parents. The yaught was destroyed and Piers crashed on Caladan, however the cymeks continued to pursue him.
Piers initially managed to lose his pursuers in the icy landscape when suddenly a Zensunni Caladan primitives' tribe, led by Tiddoc, saved his life. They had devised methods with combined attacks, to disable cymeks even with primitive tools. The next day, Agamemnon himself with 3 cymeks assaulted the village. Agamemnon grabbed Piers who tried to distract him, when they both fell in a gayser. Agamemnon's brain canister was ejected in space and Piers suffered serious bruises.
Knowing that he would find no way back to the League words, Piers spent the rest of his life with the Zensunni. Since he was presumed dead ever since, the Harkonnen heritage passed to his younger brother.