The Demigod Files
Clarisse La Rue is given the chore of taking care of Ares's war chariot. It is stolen by her immortal brothers as a prank, Deimos and Phobos (gods of terror and fear respectively). Percy and Clarisse find it at a zoo. They face the two gods, whom without their powers of fear and terror are extremely weak in battle, (unlike the nature of Ares), and are easily defeated. They bring the chariot to Ares' Temple on the Intrepid, a battle cruiser.