" [Hazel] hissed in frustration. 'I hate eidolons. I thought Piper made them promise to stay away.'
'Oh...' Frank said, like he'd just had his own daily happy thought. 'Piper made them promise to stay off the ship and not possess any of us. But if they followed us, and used other bodies to attack us, then they're not technically breaking their vow...'
'Great,' Leo muttered. 'Eidolons who are also lawyers. Now I really want to kill them. "
― Rick Riordan , The Mark of Athena (The Heroes of Olympus, #3)