The Nightmare of Azanon
A hideous god trapped in the dream world, Dal’Quor.
Worked to summon 4 gods into the world.
Hygough-Yai – The Eye, God of Primal Fear
Right in the backyard of Fallcrest was Blackwell, where the cultists of the Mage’s Guild kidnapped the homeless and refugees who had the greatest “talent” for creating living nightmares. They used foul Dominion Crowns to force images of Hygough-Yai into their victims’ minds, building him inside an unholy temple.
Lobon – The Spirit in White, Patron of Arkovia
In the Thabel Woods, the Arkovians worshipped Lobon, unknowingly building the Old One bit-by-bit with each prayer and offering. Their prayers incubated the god-thing in the mind of their own Prince, rendering him comatose as it strained to contain the Spirit in White.
Al Kal’al – The Blasphemous Machine
In the Cayne Desert, the history of the ancient machine empire was distorted. Each time someone activated the old devices, each time someone spoke the pass phrase “Al Kal’al,” the disembodied spirits of an entire race of Warforged constructs trapped between life and death were tortured, eventually implanting the will of the Old One into their greatest enemy.
The Dweller in the Gulf
I do not know what method Photh-Subbuth is using to leech from the minds of the living and create his ally the Dweller, but if the others are any comparison it is likely insidious. The only thing that is known about “the gulf” is that it is a place that can manipulate the powers of space and time.