User blog comment:Hyperborean/"The House of Hades" – official expectations blog/@comment-16219425-20130327125617

Tartarus is a Primordial, isn't he? It would be cool if he actually talked to Percy and Annabeth while there were…inside him? Eh, weird. But yeah, Tartarus is more than just a hole in the ground, he's been existing since the beginning of time (technically, he is Chaos's son and brother of Gaea.