Fanon

Fanon, simply put, is a so-called "fact" that someone thinks is true but has no evidence of in any official material, and by some means of outstandingly complex and confusiong contrivance, gets picked up by other fans. This includes terms like Herald of Unicron. While none of there terms exist within any of the official canon of the Transformers multiverse.

From Teletraan I: The Transformers Wiki, a Wikia wiki.