The tone of “The Second Coming” is prophetic and ominous. These qualities arise through the speaker’s anticipatory mood, in which they imagine what will happen in the future. Based on the cataclysm that’s unfolding in the present moment, the speaker projects an obscure vision of what’s to come. The speaker’s vision of a “rough beast” (line 21) awakening from its twenty-century slumber is incredibly ominous. Significantly, the language of the speaker’s prophecy bears a strong resemblance to that used by Saint John the Apostle in the biblical Book of Revelation. In his prophecy of the apocalypse, Saint John envisions a darkening world that succumbs to a “great earthquake” (Revelation 6:12–13):

And I beheld when he had opened the sixth seal, and lo, there was a great earthquake; and the sun became black as sackcloth of hair, and the moon became as blood. And the stars of heaven fell unto the earth, even as a fig tree casteth her untimely figs, when she is shaken of a mighty wind.

Though he relays an experience he had in the past, Saint John describes how his vision of the future unfolded in the moment of his experience. Yeats amplifies this prophetic effect by using the present tense to relay his own ominous vision of what’s to come (lines 11–17):

                 Hardly are those words out
     When a vast image out of
Spiritus Mundi
     Troubles my sight: somewhere in sands of the desert
     A shape with lion body and the head of a man,
     A gaze blank and pitiless as the sun,
     Is moving its slow thighs, while all about it
     Reel shadows of the indignant desert birds.

Though the content is different, both passages unfold a prophetic vision that imagines future destruction already coming to pass in the present moment.