Siren

Sirens were three sea nymphs who lured sailors to their death with a bewitching song. They were formerly handmaidens of the goddess Persephone. When she was secretly abducted by Hades, Demeter gave them the bodies of birds, and sent them to assist in the search. They eventually gave up and settled on the flowery island of Anthemoessa. They now live on an island in the Sea of Monsters (which might have been the same as Anthemoessa). They are part human, and part bird. They can sing a powerful song that can force you to want to get to them, but there are mines, and sharp rocks that will kill you if you try. According to Annabeth, she wanted to hear the music to become wiser; since she is a daughter of Athena, it makes sense. Also, she wanted to hear the music that lured hundreds of men to their death, and used Percy to help her without being hurt.

Appearance
In the series, the Siren's appeared as human sized vultures, with dirty black plumage, grey talons and wrinkled pink necks. The sirens have the bodies of vultures as described by Percy. They had human heads that changed to the people you knew, always smiling reassuringly, but their mouths were always greasy and caked with the remnants of old meals if seen clearly.

In mythology, they would appear as beautiful women playing harps sitting on a rock.

The Sea of Monsters
After their close escape from Circe's island, Annabeth persuaded Percy to let her hear the Sirens so she would gain more wisdom. Percy had her tied up in rope but she managed to escape (Percy forgot to disarm her), so Percy went after her. When he touched her he saw what she saw. It was her dad and Athena sitting down together. Also there was Luke, no longer evil, sitting down gesturing her to sit next to him. In background, New York was completely redesigned by Annabeth. The buildings were made of white marble with gold windows. Percy then dragged Annabeth so low below the water's surface, she could no longer hear the song of the Sirens, freeing her from the spell And Creating a water bubble so she didn't drown. From this she learned her fatal flaw: hubris.