Let's see...

Past, Present, and Future
Time's three unseen ghosts
Yet they guard the true answer
(The one that matters most.)

Past, Present, and Future
Home to that life which tests
those that rail against fate,
those the Dragon God "blessed."

Past, Present, and Future,
Three views of the Thread,
Which then grants us entry,
Or leaves our three dead.

To what does this riddle refer?