User blog comment:MortalGeek/I think I'm starting to see it now.../@comment-13446185-20131206175652

"When misrule takes its place at the eight corners of the world

When the Brass Tower walks and Time is reshaped

When the thrice-blessed fail and the Red Tower trembles

When the Dragonborn Ruler loses his throne, and the White Tower falls

When the Snow Tower lies sundered, kingless, bleeding

The World-Eater wakes, and the Wheel turns upon the Last Dragonborn. "

-The Book of the Dragonborn

While it isn't necesarily said that Dagon is part of the prophecy, Alduin's Wall depicts a carving that shows an Oblivion gate, which is obviously referring to the Oblivion Crisis.