Megaera

Megaera is one of the three Furies. She represents grudging. Megaera was the cause of jealousy and envy, and punishes people who commit crimes, espicially marriage infidelty. Like her sisters Alecto and Tisiphone, she was born of the blood of Ouranus by Kronos.

The Lightning Thief
She goes to the beach along with Alecto and Tisiphone to collect Hades' Helm of Darkness from Percy Jackson, and sees that Percy was not responsible, Ares, Luke, and Kronos were.