It was written in Destiny's Diaries "The Twelve Will Gather in the Darkest Hour"

The flame of the rising sun.

-Sunfire (fire powers and the "rising sun" of Japan)

A cold soldier returned to his family.

-Iceman (ice powers, had also recently quit the X-Men to be with his father)

A goddess recently returned from the stars.

-Storm (weather goddess)

A father of many futures connected to a greater evil.

-Cyclops (having children such as Cable and also from the Askani timeline)

A childless mother who rose from the deep.

-Jean Grey (having no children, rose as the Phoenix)

A son of a world that may never be, spawned by a sinister plan.

-Cable (Cyclops' son from the future)

A man whose mind is his greatest ally and greatest enemy.

-Professor X (this all happened right after the Onslaught crossove)

The ruler of a world gone mad, now free of demons.

-Mikhail Rasputin (was ruler of The Hill, and alternate dimension where only the strong were allowed to survive)

A man out of time with no real future.

-Bishop (trapped in the past, unknown whether his future will exist)

A North Pole ravaged by a failing spirit, lonely half of a greater whole.

-Polaris (had been posing as Magneto)

A South Pole, weaker than believed and the heart of an empire.

-Magneto (powerless and ruler of mutant nation Genosha)

A ravaged planet, worshipped by the sands of time.

-Living Monolith (keeper of the sands of time)

A thirteenth will fall from the sky… The Chosen will know the scars of Apocalypse.

-Nate Grey (sent to Earth-616 from Age of Apocalyse, he knows Apocalypse from his reality)