The Lizard Folk (aka Lizardfolk) are an ancient reptilian race.
Background[]
In ancient times, they once owned the earth, and roamed the stars before the evolution of mammals that would become humanity. The Lizard Folk crawled out of the swamps to raise gargantuan cities and ruled the stars for untold millions of years. Their race died out, disappearing into oblivion, victims of arcane sorceries from beyond the multiverse itself. The insane and incomprehensible magics (the very sounds which cannot be conceived nor reproduced by humans) that destroyed the lizards may exist still.
Some believe, Dracula may be one of the last, if not the last, of the lizard folk. He had withdrawn into Daventry. But this is only speculation, and most believe he is an undead, vampire.
The Flying Sting may be one of the magics that lead to their destruction. The Sorcery of Old may trace back to the Lizardfolk. Paradimensional deities may have been involved with destroying their civilization too.
Behind the scenes[]
The Lizard Folk are also referred to as lizard folk, and lizardfolk throughout the KQC. They are mentioned in several chapters including The Eye Between the Worlds (which describes the history of Daventry and the "Other World"), the two chapters 'written' by Alexander (which describes their dark magic), and including the An Encyclopedia of Daventry (which goes into a bit more detail about the race, but also speculation concerning Dracula).
This maybe a Lovecraft reference, based on a number of references in Companion (including the fact that these things seem to be original race behind the magics in the The Sorcery of Old and Necronomicon, and even Iconomancy spells, which can transform or summon ancient and nameless cosmic horrors with the ability to drive humans insane). In particular they maybe references to the lizardmen in the stories The Nameless City and In the Walls of Eryx. The former is connected to Abdul Alhazred and is where he discovered the Necronomicon, and the latter involves space based lizardmen on Venus.
This may also be a direct DND reference, similar to the 'multiverse' idea. In particular it shares similarities to the Lizardfolk in the 'Spelljammer' campaign.