What monsters do they face it the water bed store in book Lightning Thief?

In Rick Riordan's "The Lightning Thief," the monsters Percy Jackson and his friends face in the Waterbed Store are Furies.

The Furies are three monstrous female figures, described as "tall, muscular women with snakes for hair and eyes that glowed like embers." They are sent by Hades to capture Percy and bring him back to the Underworld.

The Furies use their powers to terrify Percy and his friends, causing illusions and manipulating their minds. However, Percy manages to defeat them with his powers as a demigod.