As Annabeth fell through darkness, holding on to Percy, she thought about her knife. It had fallen to the depths of Tartarus before she did, and it was probably laying down there somewhere.

Suddenly, Annabeth remembered a line from the old Great Prophesy.

The hero's soul cursed blade shall reap.

Annabeth knew her dagger had been cursed. And she realized now that it was gone, forever, in Tartarus. She hoped that the curses would stay down there, and Annabeth and Percy would make it out alive.

From The House of Hades.