"The 12th dynasty was due to the emergence of a ruling family from Nubia" -- (Petrie, The Making of Egypt, 1939, p. 176)

Amenemhat I, 1st King, 12th Dynasty

(1991-1962 B.C.)

The 12th Dynasty was the most important period of the Middle Kingdom. Its founder, Amenemhat I, vizier to the last Mentuhotep (11th Dynasty), usurped the throne. Amenemhet I was the son of a priest name Sesostris, and his mother was Nofret from Ta-Seti, Nubia.

Details of the state of Egypt come from the 'Prophecy of Neferti', a text said to date from the Old Kingdom which relates how a king 'Ameny' would come to save the country! 

Then a king will come from the South, 

Ameny, the justified, my name, 

Son of a woman of Ta-Seti, child of Upper Egypt,

He will take the white crown, he will join the Two Mighty Ones (the two crowns)

Asiatics will fall to his sword, 

Libyans will fall to his flame,

Rebels to his wrath, traitors to his might, 

As the serpent on his brow subdues the rebels for him, 

One will build the Walls-of-the-Ruler, 

To bar Asiatics from entering Egypt . . .

Limestone, painted, stela of Amenemhat, 12th Dynasty, Shows the classic offering scene. 

British Museum