There is no God, and Nyarlathotep is It's messenger...

Nyarlathotep (Pronounced either ni-ar-lat-ho-tep or nyar-lat-ho-tep), also known as N'hyarlothatep, Naralythotep, The Crawling Chaos and The Haunter in the Dark, is one of the cosmic Outer Gods in the Cthulhu Mythos based on the writings of H. P. Lovecraft.

Nyarlathotep differs from the Outer Gods in a number of ways. Most of them are exiled to stars and the places between them, like Yog-Sothoth and Azathoth, or sleeping and dreaming like Cthulhu; Nyarlathotep, on the other hand, is active and constantly walking the Earth in the guise of a human being, usually a tall, slim, joyous man. Most of them have their own cults serving them, while Nyarlathotep seems to serve them and take care of their affairs in their absence. Most of them use strange alien languages, while Nyarlathotep uses human languages and can be mistaken for a human being. Finally most of them are powerfully destructive, while Nyarlathotep seems to prefer  using deception, manipulation and even propaganda to achieve his goals. At that he is probably the most human-like among them.

Nyarlathotep enacts the will of the Outer Gods, and is their messenger, heart and soul; he is also a servant of Azathoth, whose wishes he immediately fulfills and the one member of the Mythos who deals on a personal level with human beings in general. Unlike the other Outer Gods, causing madness is more important and enjoyable than death and destruction to Nyarlathotep. He is described as the very soul of "gigantic, tenebrous, ultimate gods – the blind, voiceless, mindless gargoyles" which make up the Mythos. As such, his evil is absolute, for he is not only the servant of these creatures, but their very consciousness. Nyarlathotep has appeared through the range of time, from ancient Egypt where he instructed Nephren-Ka in the arts of the darkest magic, up until modern day, where one might find him traveling and spreading his terror where any will listen. Wherever he visits, rest vanishes and the wails of nightmares untold echoes through the streets. Nyarlathotep is especially fond of technology and psychology. Nyarlathotep delights in spreading chaos and destruction amongst humanity. In the Mythos, he is the being who acts to initiate humans into the Mysteries, and acts as the interface between humanity and the alien forms of the other Old Ones.

Nyarlathotep has been identified with the 'Black Man' of traditional Witchcraft; with the medieval Devil, and with the Thelemic entity Aiwass, whom Crowley describes as: A tall dark man in his thirties, with the face of a savage king, and eyes veiled lest their gaze should destroy what they saw. Nyarlathotep has many different forms (some literature refers to these forms as Masks, and says that he has a thousand of them), and is thus known by many different avatars, but his key appearances are in human form...

The Masks of Nyarlathotep:

Ahtu (Congo) In this form, Nyarlathotep appears as a huge mound of viscous material, with several golden tentacles sprouting from its central mass. Ahtu’s worshipers are usually deformed or mutilated natives. He is called by using a golden bracelet usually separated innto two parts, to prevent Ahtu from being summoned by accident.
The Beast (Egypt) This form manifests itself only at one particular place in Egypt. It was the focus of a revolutionary cult in the Fourteenth Dynasty.
The Black Demon This is a black-furred, snouted monster which is destroyed by light. The being may be controlled by a summoner using certain talismans, though the user runs the risk of being attacked herself.
The Black Man In legends about witchcraft, the Black Man was the being that sealed pacts between the Devil and witches; in the Cthulhu Mythos, it is Nyarlathotep who fills this role.
Black Pharaoh (Egypt) A hairless man with dead black skin and hooves for feet. He is connected with the witch-cults of Western Europe.
Black Wind (Africa) At times, Nyarlathotep takes the form of the Black Wind, a great storm that can destroy crops, forest, and houses for miles around when he manifests.
Bloated Woman (China) In this form, Nyarlathotep appears as a huge, obese woman with five mouths and many tentacles. It carries the mystical Black Fan, with which it hides its unseemly bulk from humans until it has ensnared them.
Bringer of Pests (Egypt) Worshiped in Egypt’s Twelfth Dynasty, this manifestation can only be described as a horde of huge spitting supernatural locusts. It is worshiped today by a group known as the Knights of the Silver Twilight.
Dark Demon A form of Nyarlathotep that occasionally manifests itself through a contactee. It appears much as the Black Demon, but is larger and more cunning. It sometimes calls to those steeped in studies of black magic, promising them glory if they will allow him to enter their bodies. Of course, no reward comes to those possessed by this form of Nyarlathotep.
Effigy of Hate (Africa) The Mighty Messenger was worshiped by one African tribe, to which he manifested himself through their war totems. This form is known to have some control over time.
The Faceless God (Egypt) In the elder days of the Egyptian civilization, Nyarlathotep was worshiped in the form of a winged sphinx with a featureless head which bore the triple crown of a god. The Faceless God was known to manifest itself through its idols. This cult was later suppressed by the other priesthoods, becoming nearly forgotten in the millennia following its dissolution.
The Floating Horror (Haiti) This form of Nyarlathotep must manifest itself through the body of a specially prepared host. It appears as a red veined jellyfish-like floating organism of a bluish color. This avatar is connected with certain fringe voodoo cults.
The God of the Bloody Tongue: A creature the size of a building, of vaguely humanoid stature but having three legs and immense, clawed arms. Its head is an immense blood-soaked tentacle in which a vast, gaping maw looms when the thing howls at the moon.
Haunter of the Dark A bloated, batlike creature with a single, burning, three-lobed eye that appears able to kill by fear alone. Like the Black Demon, it is destroyed by light.
The Messenger of the Old Ones (It is not known if this refers to a true form of Nyarlathotep or is merely a title)
Mr. Skin An immaculately dressed pimp. Unlike some other “Black Man” forms, this is wholly and unmistakably human, and appears to be a perfectly normal African American. He is closely associated with a cult of Shub-Niggurath.
Narla An extremely sophisticated and detailed virtual reality simulation of a very beautiful white woman, this form invades Computer  systems. Her appearance is designed to distract the (typically male) sysadmin long enough for her to wrest total control of the system from him. Anyone using such a system when Narla invades is in very serious trouble.
Shugoron (Malaysia) A black humanoid figure represented as playing a sort of horn. This being is revered by the Tcho-tcho people of Malaysia.
The Small Crawler (India) A dwarfed human figure, with four arms and three tentacles for legs. Little else is known of him, except that he is mentioned in the Cthaat Aquadingen.
The Thing in the Yellow Mask An entity draped in yellow silk, its only known manifestation occurred within the abandoned city of ’Ygiroth on Mount Lerion. (Possible link to the King in Yellow?)
Wailing Writher A column of whirling black tentacles and screaming mouths, it is alluded to in some Hindu tales.
Xipe Totec (Mesoamerica) In the guise of a flayed, skinless corpse, Nyarlathotep was worshiped among the Aztecs (also called the Skinless One).

The Crawling Chaos

Some texts state that the Crawling Chaos is another name for the end of the world. One individual described it as the ceaseless pounding of the waves of a dark ocean that eats away endlessly at the earth until finally nothing is left. When this occurs then our world ends, swallowed finally by Chaos into the abyss of nothingness. The name more likely describes the Chaos at which Azathoth rules from the center, and how his power of consumption spreads out like waves, devouring all that stands in its way until nothing is left.

Most however,  state that the Crawling Chaos is another name for Nyarlathotep. This theory may have basis in fact, for Nyarlathotep is the messenger of Azathoth and spreads his will throughout the realm of reality. By doing so, he is acting as the waves of Chaos, spreading from the center to destroy all.

Quotes

"What his fate would be, he did not know; but he felt that he was held for the coming of that frightful soul and messenger of infinity's Other Gods, the crawling chaos Nyarlathotep." -- H.P. Lovecraft, The Dream-Quest of Unknown Kadath

"There was the immemorial figure of the deputy or messenger of hidden and terrible powers - the 'Black Man' of the witch cult, and the 'Nyarlathotep' of the Necronomicon." -- H.P. Lovecraft, The Dreams in the Witch House

"There are references to a Haunter of the Dark awaked by gazing into the Shining Trapezohedron, and insane conjectures about the black gulfs from which it was called. The being is spoken of as holding all knowledge, and demanding monstrous sacrifices." -- H.P. Lovecraft, The Haunter of the Dark

One of earliest human myth cycles is that of the dark trickster. This stranger appears without warning, and before he leaves, the world has been irrevocably changed. Sometimes this change seems for the better, but more often it is change for the worst. The trickster brings confusion and chaos into the world of people, who therefore dread his visitations. Modern men believe him to be the boogey-man of simpler, more primitive minds. There are those of us who know otherwise — those who still fear that the trickster will once again visit our world and change it, forever. -- From the memoirs of R.L. Cullinan

Nyarlathotep
by H. P. Lovecraft
Published November 1920 in The United Amateur

Nyarlathotep... the crawling chaos... I am the last... I will tell the audient void...

I do not recall distinctly when it began, but it was months ago. The general tension was horrible. To a season of political and social upheaval was added a strange and brooding apprehension of hideous physical danger; a danger widespread and all-embracing, such a danger as may be imagined only in the most terrible phantasms of the night. I recall that the people went about with pale and worried faces, and whispered warnings and prophecies which no one dared consciously repeat or acknowledge to himself that he had heard. A sense of monstrous guilt was upon the land, and out of the abysses between the stars swept chill currents that made men shiver in dark and lonely places. There was a demoniac alteration in the sequence of the seasons the autumn heat lingered fearsomely, and everyone felt that the world and perhaps the universe had passed from the control of known gods or forces to that of gods or forces which were unknown.

And it was then that Nyarlathotep came out of Egypt. Who he was, none could tell, but he was of the old native blood and looked like a Pharaoh. The fellahin knelt when they saw him, yet could not say why. He said he had risen up out of the blackness of twenty-seven centuries, and that he had heard messages from places not on this planet. Into the lands of civilization came Nyarlathotep, swarthy, slender, and sinister, always buying strange instruments of  glass and metal and combining them into instruments yet stranger. He spoke much of the sciences of electricity and psychology and gave exhibitions of power which sent his spectators away speechless, yet which swelled his fame to exceeding magnitude. Men advised one another to see Nyarlathotep, and shuddered. And where Nyarlathotep went, rest vanished, for the small hours were rent with the screams of nightmare. Never before had the screams of nightmare been such a public problem; now the wise men almost wished they could forbid sleep in the small hours, that the shrieks of cities might less horribly disturb the pale, pitying moon as it glimmered on green waters gliding under bridges, and old steeples crumbling against a sickly sky.

I remember when Nyarlathotep came to my city the great, the old, the terrible city of unnumbered crimes. My friend had told me of him, and of the impelling fascination and allurement of his revelations, and I burned with eagerness to explore his uttermost mysteries. My friend said they were horrible and impressive beyond my most fevered imaginings; and what was thrown on a screen in the darkened room prophesied things none but Nyarlathotep dared prophesy, and in the sputter of his sparks there was taken from men that which had never been taken before yet which showed only in the eyes. And I heard it hinted abroad that those who knew Nyarlathotep looked on sights which others saw not.

It was in the hot autumn that I went through the night with the restless crowds to see Nyarlathotep; through the stifling night and up the endless stairs into the choking room. And shadowed on a screen, I saw hooded forms amidst ruins, and yellow evil faces peering from behind fallen monuments. And I saw the world battling against blackness; against the waves of destruction from ultimate space; whirling, churning, struggling around the dimming, cooling sun. Then the sparks played amazingly around the heads of the spectators, and hair stood up on end whilst shadows more grotesque than I can tell came out and squatted on the heads. And when I, who was colder and more scientific than the rest, mumbled a trembling protest about imposture and static electricity, Nyarlathotep drove us all out, down the dizzy stairs into the damp, hot, deserted midnight streets. I screamed aloud that I was not afraid; that I never could be afraid; and others screamed with me for solace. We swore to one another that the city was exactly the same, and still alive; and when the electric lights began to fade we cursed the company over and over again, and laughed at the queer faces we made.

I believe we felt something coming down from the greenish moon, for when we began to depend on its light we drifted into curious involuntary marching formations and seemed to know our destinations though we dared not think of them. Once we looked at the pavement and found the blocks loose and displaced by grass, with scarce a line of rusted metal to show where the tramways had run. And again we saw a tram-car, lone, windowless, dilapidated, and almost on its side. When we gazed around the horizon, we could not find the third tower by the river, and noticed that the silhouette of the second tower was ragged at the top. Then we split up into narrow columns, each of which seemed drawn in a different direction. One disappeared in a narrow alley to the left, leaving only the echo of a shocking moan. Another filed down a weed-choked subway entrance, howling with a laughter that was mad. My own column was sucked toward the open country, and presently I felt a chill which was not of the hot autumn; for as we stalked out on the dark moor, we beheld around us the hellish moon-glitter of evil snows. Trackless, inexplicable snows, swept asunder in one direction only, where lay a gulf all the blacker for its glittering walls. The column seemed very thin indeed as it plodded dreamily into the gulf. I lingered behind, for the black rift in the green-litten snow was frightful, and I thought I had heard the reverberations of a disquieting wail as my companions vanished; but my power to linger was slight. As if beckoned by those who had gone before, I half-floated between the titanic snowdrifts, quivering and afraid, into the sightless vortex of the unimaginable.

Screamingly sentient, dumbly delirious, only the gods that were can tell. A sickened, sensitive shadow writhing in hands that are not hands, and whirled blindly past ghastly midnights of rotting creation, corpses of dead worlds with sores that were cities, charnel winds that brush the pallid stars and make them flicker low. Beyond the worlds vague ghosts of monstrous things; half-seen columns of unsanctified temples that rest on nameless rocks beneath space and reach up to dizzy vacua above the spheres of light and darkness. And through this revolting graveyard of the universe the muffled, maddening beating of drums, and thin, monotonous whine of blasphemous flutes from inconceivable, unlighted chambers beyond Time; the detestable pounding and piping whereunto dance slowly, awkwardly, and absurdly the gigantic, tenebrous ultimate gods the blind, voiceless, mindless gargoyles whose soul is Nyarlathotep.