User blog comment:Percy Jackson12/The Seven/@comment-99.35.14.156-20111018004002/@comment-3146930-20111019204656

The Titans arent gone, the Titans working for Kronos were defeated. There is a difference. Only a handful of Titans were working for Kronos which means that the Titans still exist as several of them sided with Olympus during the first war (like Prometheus). Once Kronos was defeated during the second war in NYC, they went into hiding while Percy asks the gods that any peaceful Titans or ones not involved in the first war be set free from their prisons as part of his final wish. So they arent just gone.