Poseidon's Pearls

Poseidon's Pearls are three pearls that Poseidon gives to Percy, Annabeth, and Grover.

The Lightning Thief
In The Lightning Thief, as Percy jumps into the Mississippi River, a Naiad tells Percy to go to Santa Monica. When he arrives, the naiad gives him the pearls saying they are from his father. Percy takes the pearls to the Underworld, and when Hades tries to kill them, they smash the pearls at their feet. The pearls then carry them to the sea.