The Final Fantasy XIV's site has been updated with a small preview of one of the three towering pillars, named Sephirot. Sephirot will require a part of eight players to defeat and is available in normal and extreme difficulty.
Sephirot, the Fiend, was a deity once worshipped by a tree-like race native to Meracydia. Brought into being for the sole purpose of repelling the Allagan invasion, Sephirot inflicted ruinous losses upon the imperial army before finally being subdued and imprisoned in the central facility of Azys Lla. And now, millennia later, this immensely powerful entity threatens to awaken, his vengeful dreams disturbed by the careless ambitions of Archbishop Thordan VII. Topple the first pillar of the Warring Triad, or wheresoever his colossal shadow falls shall be visited by unthinkable catastrophe!
You can find out more by visiting Final Fantasy XIV: Heavensward site.