Pericylmenus was gifted the ability to shapeshift into various animals from his grandfather Poseidon. When Hercules waged war against Neleus, king of Pylos, for refusing to purify Hercules for the murder of Iphitus, Hercules killed eleven of the twelve sons of Neleus, one of which was Periclymenus. With the assistance of Athena, Hercules recognized Periclymenus as a bee, settled upon the yoke of his chariot and shot him with an arrow.
Periclymenus' family survived on and inherited his gift of shapeshifting, a unique gift given to only the Argonaut by Poseidon. Over the following millennia, Periclymenus' descendants came to include the Zhang family, some of whom would be associated with Camp Jupiter and New Rome. Others remained on the island of Pylos, hanging out in an ancient stronghold where the ancient king of Pylos had supposedly stored his treasure in times of crisis.
Frank Zhang and the rest of his family are descendants of Periclymenus. Every member of his direct family are able to transform into animals as Periclymenus passed down this ability. After Frank learns about his lineage, he tells Percy Jackson that they are related, much to Percy's, Hazel's, and later Tyson's, surprise.
In an attempt to find the Pylosian Mint, Piper McLean charmspeaks an Ancient Greek ghost into revealing the location of an ancient stronghold where Periclymenus' shapeshifting descendants supposedly hang out. Frank heads up to the cave alone and his cousins give him the poison that he needs. Frank tells Piper that his cousins have been living on Pylos for generations, all descended from Periclymenus the Argonaut and that he'd told them the story of his own branch of Periclymenus's family. However, they had acted cold and distant, stating that long-lost relatives returning to Pylos had happened before and Frank believes that they didn't want him around, not liking that he's also the son of Mars and possibly not liking that he's of Chinese descent. Along with the Pylosian mint, Periclymenus's descendants give Frank a clue on where they can find the next ingredient for the Physician's Cure.
- Shapeshifting: Periclymenus has the ability to change into any animal he wishes, either mythical or real. He was gifted this ability by his grandfather Poseidon.