Old Gods
Ancient failed conceptual experiments performed by the first Harolds themselves. Old Gods are strange Semi-Concepts, distorted, wrong, eldritch experiments that rebelled against their creators without ever knowing they were created.
Now they're multiversal in scale, some have even become full Concepts, like Yig: father of serpents or Atlach-Nacha: mother of spiders.
Most, however, simply adapted to existence after they were abandoned.
The most well-known, Cthulhu, has been inflicting visions across the Multiverse to make sure even the less active Old Gods remain Semi-Concepts. One of these men was named Howard Phillips Lovecraft, and he took the idea and ran with it.
The most truly infamous of them, Nyarlathotep, wanders the multiverse in black pharaoh's garb. Some call them the god of snake oil salesmen; others call him the bureaucrat of the apocalypse.
Many worship Shub-Niggurath, The Black Goat with a Thousand Young, a thousand is most likely a very low estimate by now. This fertility god of confusing gender identity is well known for having strange children with its priests.
The Blind Idiot God, Azathoth, was lobotomized in the experiments from ages passed. This reduced his intelligence to that of a rabid dog. Now, the Salpinx play her music from within Yog-Sothoth to keep Azathoth asleep. He constantly dreams up new realms within her sleep, realms she would tear asunder if he ever woke up.
