The Traitor's Stylus

There is a Human myth about a traitor in the past who, despite his treachery - and maybe even because of it - managed to avert a disaster in the world. 
He is said to have used a scrap of sacred knowledge, a secret spell spoken and a single sigil scored with a stylus on a piece of stone. The stylus in the myth is known by different names in different versions of the tale, but all agree that it was a small, pointed metal blade that could be used to carve a piece of stone.

Summary

A great danger threatened the very existence of the world from the space between the planes of reality. The prime material plane was to be devoured, and the people of the world would become eternally tormented slaves of an unknown power.
Only one chance remained: a human who had been a traitor to his race came to understand the nature and the name of the danger that approached. With this sacred knowledge, a spell he learned from a power from another plane and a secret sigil that he carved on a rock at the origin of the danger, he caused the danger to subside, perhaps forever. He died in the saving of the world, atoning for his treachery.

Historical Basis

The historical basis for this myth is contested, with many scholars contending that the myth is either of pre-human origin or that it was brought to Westlo with the first human arrivals. Others point to the missing history regarding a human Provost of Hollymargret. The most popular interpretation is that it is a prophecy of the coming of Pater Ty Holan, his origin as the son of a priest of a foreign deity being his 'treachery', and the reinstitution of the Denrach faith as the aversion of a world-threatening danger.

Spread

The myth is well-known throughout the humanfolk of Westlo, and it is taught in schools. Most explanations for the Stylus are that the Traitor of the Tale used a magical dagger to make his inscription in the stone that brought an end to the danger that threatened the world. The sigil inscribed is interpreted by glossarians to be the stylised 'cube' of Dendrah, but in every version of the myth the sigil is explicitly 'secret'.

Variations & Mutation

As far as the Traitor's Stylus is concerned, there are few variations in the telling of the tale. The one unusual feature is that the name given to it is sometimes changed to Knife or even Penknife, which may be a pun based on the fact that he used the object to write on the stone.
The other variation that is recorded is that the Stylus itself had a history before the Traitor used it, and it was called the Poetaster's Stylus or the Bard's Blade. 
The size of the blade varies, but all agree that it is too small to be useful as a weapon to a human, so it is initially rejected as a powerful artifact, and the Traitor only uses it as a final resort.