AKA: The Mighty Messenger, the Herald of Azathoth, The Crawling Chaos, the Thousand Faced, The Mask that Mocks, etcetera.

Nyarlathotep, the False Messenger, is unique among the known Great Old Ones in that he has succeeded in ascending and claiming a place in this Universe's Invisible Clergy. He is honoured by all the other Qelipoth as their Herald, the One who has shown the way to reconquer the cosmos and shape it more to their liking.

When this cataclysmic event occurred is unknown, but a likely candidate is Nephren-Ka, the Black Pharoah of Egypt, Godwalker of Nyarlathotep, who was presumably able to compel the mass belief of his subjects to a sufficient extent that Ascension became possible.

Still, Nyarlathotep's position in the Clergy is hardly secure. His throne is carved from a contested domain between The Messenger and The Trickster, both of whom desire to see him cast down, and in this they are supported by the Comte and possibly by The Cruel Ones. Without a pantheon of other Ascended Great Old Ones to support him, Nyarlathotep is like a keystone without an arch. As a result, his Godwalker and Avatars are constantly called upon to support the endeavours of the other Great Old Ones to arise from their deaths, and to defeat the plots of the other Clergy to dethrone him.

Furthermore, due to the active possibility of Ascension, Nyarlathotep is plagued by the same kind of murderous rivalries amongst his Avatars that affect the other Invisible Clergy. Unlike Great Cthulhu, Mordiggian, Yig-Tsatthogua, Ithaqua or Hastur, Nyarlathotep has succeeded in becoming a human god, but this has also humanised him. He cannot call upon legions of soul-devoured monsters for support, only the quarrelsome individual humans who tread in his footsteps.

Masks, Symbols and Signs: Nyarlathotep contests the Greco-Roman Hermes with The Messenger, for it should not be forgotten that Hermes is the god of liars and thieves as well as messengers and merchants. Hermes is identified with the planet Mercury, but Nyarlathotep is symbolised by the mysterious Yuggoth, which may be Pluto, Persephone, Nemesis, or some as-yet-unknown celestial body. Aztec Tezcatlipoca, Egyptian Thoth and Norse Loki are other masks Nyarlathotep wishes to claim as his own. Elaborate masks, the Caduceus, Sphinxes, and the great wild cats, such as jaguars and panthers, also have an affinity with Nyarlathotep.

Taboos: Avatars of Nyarlathotep can never tell the whole, plain, unvarnished truth, and if they happen to know the truth about something they should act to discredit it. They must always twist what they say to advance themselves and/or the Great Old Ones. They must actively oppose Avatars of The Messenger, The Trickster and The Comte if they come across them.

The Archetype in History: After the reign of Nephren-Ka and the worship of Thoth, Nyarlathotep is believed to have been worshipped as The Black Man by European witch-cults, and used to link them across the continent. In 1578 a new Godwalker, Hernando Joaquin de Tristero y Calavera, seized control of the remnants of the network that had survived the witch-burning frenzies and attempted to create a supernaturally empowered postal system to rival Thurn & Taxis, the Europe-wide Imperial Mail Service and servants of The Messenger. Whether he succeeded, and what became of the network, is unknown.

The most likely current candidate for Godwalker is a Duke in New York named Steven Alzis. He totally denies it, which (to some people) proves it must be true. It's also been suggested that in fact the most recent Godwalker was Jacques Derrida, who convinced many that there was not only no such thing as a true message, but there was no "truth" for a "message" to "be".

Eastern Cryptomancy is a logical choice of Magical School for Avatars of Nyarlathotep.

Channels:
1-50%: I'm Just The Messenger.
With a successful roll, you cause someone to whom you have told something to forget that they heard it from you.
Though subtle, this channel can be quite powerful, due to the tendency of the human memory to "fill in" missing elements, and therefore to fill in some other source for the information. Those who are trained in careful checking of their facts (e.g. good academics, intelligence analysts, etc) are harder to affect. To see how reliable the victim considers the information, use this formula: If the Avatar roll was below the victim's Mind stat, it's given the status of rumour, pub gossip, mention in a suburban newspaper, or other unsubstantiated source. If the roll is above the victim's Mind stat, they believe that they worked it out themselves, or they heard it from a trusted source (best friend, peer-reviewed journal, etc).

51-70%: Don't Shoot The Messenger.
After the Avatar has informed someone of something and successfully made an Avatar roll, the informee must succeed in a Soul roll to attack or otherwise express hostility towards the Avatar. No point in shooting the messenger.

71-90%: Bad News Travels Fast.
The Avatar can invoke this power to be the first to the destination with the information, whatever it is, as long as it's bad news (or rather, can be spun as bad news, considering the Avatar's taboo). Like the Pilgrim channel, the time and space between source and destination passes in a blur. No-one else can be "carried along" using this effect. Using this effect to beat Avatars of The Messenger or The Pilgrim to a destination is one way to advance rapidly in Nyarlathotep's favour.

Nyarlathotep has needs. Like cosmic survival. To advance from 90% to 91%, and for every increase thereafter, it is necessary to either ritually sacrifice, or successfully subject to the power of the Crawling Chaos, a conscious (usually implying a rating above 50%) Avatar of The Messenger or The Trickster (or another Archetype that is directly opposed to Nyarlathotep).

91-98%: Crawling Chaos/Tryst with Tristero
On a successful roll, the Avatar can tell what a victim's biggest psychological weakness is (in game terms, in which Madness Meter they have the most Failed notches) and can craft a lie targeted to exploit that weakness. This triggers an automatic Madness Meter check in the victim. In addition, if the Avatar roll is also above the victim's Mind score, then the victim is plunged into a paranoid state in which they see confirmation of the lie in everything around them. They will frequently abandon whatever else they are doing, instead beginning an obsessive hunt to confirm or disprove the lie.

The Godwalker of Nyarlathotep is believed to always take on the same power, the Thousand Faces. Every new Godwalker of Nyarlathotep becomes able to take on the form of all previous Godwalkers, including non-humans from previous, dead universes. This is because the souls (Demons) of previous Godwalkers are eternally bound into service to the current one (but that won't happen to you, 'cos no-one's ever going to trick you out of Godwalkerhood, right?). In conjunction with the Third channel, this often enables the Godwalker to maintain many identities at once.

Disclaimer: I only have UA 1st edition. This doesn’t include The Messenger. Apologies if I’ve reinvented the wheel (as I apparently did with Herpemancy & Yig-Tsathoggua. What's a snake school doing in a book about burger-flipping?).