The Spectral Horseman.

Posthumous Fragments Of Margaret Mcholson.
Being Poems found amongst the Papers of that noted Female who attempted the life of the King in 1786. Edited by John Fitzvictor.
[The "Posthumous Fragments", published at Oxford by Shelley, appeared in November, 1810.]
The Spectral Horseman.
What was the shriek that struck Fancy's ear
As it sate on the ruins of time that is past?
Hark! it floats on the fitful blast of the wind,
And breathes to the pale moon a funeral sigh.
It is the Benshie's moan on the storm,
Or a shivering fiend that thirsting for sin,
Seeks murder and guilt when virtue sleeps,
Winged with the power of some ruthless king,
And sweeps o'er the breast of the prostrate plain.
It was not a fiend from the regions of Hell
That poured its low moan on the stillness of night:
It was not a ghost of the guilty dead,
Nor a yelling vampire reeking with gore;
But aye at the close of seven years' end,
That voice is mixed with the swell of the storm,
And aye at the close of seven years' end,
A shapeless shadow that sleeps on the hill
Awakens and floats on the mist of the heath.
It is not the shade of a murdered man,
Who has rushed uncalled to the throne of his God,
And howls in the pause of the eddying storm.
This voice is low, cold, hollow, and chill,
'Tis not heard by the ear, but is felt in the soul.
'Tis more frightful far than the death-daemon's scream,
Or the laughter of fiends when they howl o'er the corpse
Of a man who has sold his soul to Hell.
It tells the approach of a mystic form,
A white courser bears the shadowy sprite;
More thin they are than the mists of the mountain,
When the clear moonlight sleeps on the waveless lake.
More pale HIS cheek than the snows of Nithona,
When winter rides on the northern blast,
And howls in the midst of the leafless wood.
Yet when the fierce swell of the tempest is raving,
And the whirlwinds howl in the caves of Inisfallen,
Still secure mid the wildest war of the sky,
The phantom courser scours the waste,
And his rider howls in the thunder's roar.
O'er him the fierce bolts of avenging Heaven
Pause, as in fear, to strike his head.
The meteors of midnight recoil from his figure,
Yet the 'wildered peasant, that oft passes by,
With wonder beholds the blue flash through his form:
And his voice, though faint as the sighs of the dead,
The startled passenger shudders to hear,
More distinct than the thunder's wildest roar.
Then does the dragon, who, chained in the caverns
To eternity, curses the champion of Erin,
Moan and yell loud at the lone hour of midnight,
And twine his vast wreaths round the forms of the daemons;
Then in agony roll his death-swimming eyeballs,
Though 'wildered by death, yet never to die!
Then he shakes from his skeleton folds the nightmares,
Who, shrieking in agony, seek the couch
Of some fevered wretch who courts sleep in vain;
Then the tombless ghosts of the guilty dead
In horror pause on the fitful gale.
They float on the swell of the eddying tempest,
And scared seek the caves of gigantic...
Where their thin forms pour unearthly sounds
On the blast that sweets the breast of the lake,
And mingles its swell with the moonlight air.