A special flower that resembles a carnation, though being a sickly-yellow color. Persephone gave Percy, Nico, and Thalia this flower to track Ethan Nakamura, who had stolen the Sword of Hades from her husband, Hades, while it was being forged. The flower would always point in his direction and the petals would die and drop off as he got closer to escaping the Underworld. It finally died when he released the Titan Iapetus. It is unknown what else it can do as this particular flower was created to only track Ethan.
After completing the mission, Persephone gave each of the demigods a red rose that, when crushed, would return them to the land of the living. These were similar to Poseidon's Pearls (in the movie, Persephone's pearls). Only Percy and Thalia used theirs as Nico wanted to stay in the Underworld, but could also leave by shadow traveling.