Opium.

On reading De Quincey's "Confessions of an Opium Eater."
I seemed to stand before a temple walled
From shadows and night's unrealities;
Filled with dark music of dead memories,
And voices, lost in darkness, aye that called.
I entered. And, beneath the dome's high-halled
Immensity, one forced me to my knees
Before a blackness, throned 'mid semblances
And spectres, crowned with flames of emerald.
Then, lo! two shapes that thundered at mine ears
The names of Horror and Oblivion,
Priests of this god, and bade me die and dream.
Then, in the heart of hell, a thousand years
Meseemed I lay, dead; while the iron stream
Of Time beat out the seconds, one by one.