There are just as many known Ancients as there are, presumably, unknown -- the Ancients we've seen and read about are just a smattering of what may potentially be out there. Agamaggan, the great boar, patron god of the quillboar. Aessina, the wild and untamed spirit of nature and the forests. Aviana, ferocious heart of the winged creatures that populate the world. Cenarius, Goldrinn, Malorne, Omen, Tortolla, Ursoc, Ursol -- all have their own purposes, strengths, and weaknesses. All have been charged with guarding aspects of the world.
Along the same vein, we have the Celestials -- Yu'lon, the jade serpent of wisdom, Chi-Ji, the red crane of hope, Xuen, the white tiger of strength, and Niuzao, the black ox of stubborn persistence. Each Celestial protects Pandaria in its own way. In fact, the Celestials were responsible for locking the Vale of Eternal Blossoms away, and they choose its defenders from the mortals of Pandaria. Once chosen, these protectors of the Vale must leave whatever prior life they may have led, and dedicate themselves fully to buy cheap wow gold and guarding the Vale's secrets and keeping them safe.
It's been stated before that the Celestials are Pandaria's equivalent of the Ancients -- they're simply a lot more active and a lot less reclusive than the Ancients we've encountered thus far in game. In fact, it took a full-out assault on Hyjal to bring most of these Ancients back into play. By and large, the Ancients of Azeroth have been one of those interesting mysteries of Azeroth's history -- they are there to buy world of warcraft accounts and protect and guard different aspects of the world.