Most likely passage for the test:
O sages standing in God's holy fire
As in the gold mosaic of a wall,
Come from the holy fire, perne in a gyre,
And be the singing-masters of my soul.
Consume my heart away; sick with desire
And fastened to a dying animal
It knows not what it is; and gather me
Into the artifice of eternity.
Context: Yeats, dealing with his own mortality, decides he will sail for Byzantium (Istanbul), which he viewed as a center for artists. His body is a "dying animal," but his heart will be consumed and he will be transformed into an "artifice of eternity" -- freeing him from his mortality and allowing him to live forever as art.