Befouled by an acrid and blinding pool of green slime, this horrible scene of desolation found in an empty lot at the base of Potrero Hill is all that remains after an unanticipated and devastating visit by Cthulhu, the Ancient One.
On a moonless night in November 1969 a crowd of supplicants had gathered for their monthly worship of the Old Ones and their spawn. The priest stood before the green onyx altar, bowing to the Emerald Kingdom of Great Cthulhu and summoning the Ancient Ones forth from their black abyss.
As the celebrants chanted the terrible words, Ph'nglui mglw'nafh Cthulhu R'lyeh wgah'nagl fhtagn, ("In his house at R'lyeh dead Cthulhu waits dreaming,") insane shouts and harrowing screams broke out as a pulpy, tentacled head surmounting a grotesque and scaly body with rudimentary wings emerged from a foul drain pipe running from the basement of the building into the Bay of San Francisco.
The monster emerged from its from its aeon-long imprisonment, visibly darkening the sky as it opened its flapping membraneous wings, then squeezed its sickening, gelatinous green immensity into the ceremonial chamber. The odour rising from the newly opened depths was intolerable, and the assembled congregation fell down dead, their strangulated bodies dripping with green ooze, their faces paralyzed in mortal terror.
The room was befouled by an acrid and blinding green cloud as the venomous creature, seething with a fearsome and unnatural malignancy, squeezed its disgusting mass back into the drain from which it had emerged and slithered back into the Bay.
"What has risen may sink, and what has sunk may rise. Loathsomeness waits and dreams in the deep, and decay spreads over the tottering cities of men."
(H.P. Lovecraft, 1926)