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. Unlike the other Outer Gods, causing madness is more important and enjoyable than death and destruction to Nyarlathotep.
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:
* Ahtu: a huge mound of viscous material with several golden tentacles; this form is peculiar to the Congo.
* The Black Demon: a black-furred, winged and snouted monster. The creature is destroyed by light.
* The Dark Demon: a larger, more cunning version of the Black Demon.
* The 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 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.
* Shugoran: a black humanoid figure playing some sort of horn, this form is worshiped by the Tcho-tcho people of Malaysia.
* The Dark Pharaoh: a hairless man with dead black skin and hooves for feet; this form is peculiar to Egypt. This form and the previous two appear to be slight variations on the same Mask.
* The Bloated Woman: a hugely obese woman with five mouths and many tentacles; this form is peculiar to China.
* The Faceless Sphinx
* The Father of Knives
* The Father of Locusts (Bringer of Pests): a horde of huge, spitting supernatural locusts.
* The Beast of the Lashing 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.
* The Messenger of the Old Ones (It is not known if this refers to a true form of Nyarlathotep or is merely a title)
* The Crawling Chaos
* The Small Crawler: a small human figure with four arms and three tentacles for legs.
* The Wailing Writher: a column of writhing black tentacles and screaming mouths.
* Xipe Totec (also called the Skinless One): a flayed, skinless corpse worshiped as a god by the Aztecs.
"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 civilisation 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 a nightmare." -- H.P. Lovecraft, Nyarlathotep
"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