ANSWER:
In the lines 18-19 of the poem “The Second Coming” the sleeper is "the spirit of pagan savagery "
EXPLANATION:
The lines 18-19 are present in the second stanza of the poem. These lines denote the essence of barbarianism that existed before the origin of Christianity, and during the Christian era, it was in deep sleep. But now, the era of Christianity is going to perish, and a new era begins characterized by barbarianism.
