"Deep Suelise" is my best guess at what you would call a native of a place called "Deep Suel".

Deep Suelian? Deep Suelist? Deep Sueli?

Long story short - GM took the "Deep Imaskari" civilization (Forgotten Realms - detailed in "Underdark"; A highly magical civilization that fled into a giant cavern and mystically sealed themselves off from any contact thousands of years ago) and transplanting it into ... Was it Greyhawk? I'm not recalling, but there is a campaign setting out there that has the ancient nation of Suel...

Had forgotten that it was two campaign backgrounds conflated, or I would have put that in the first post, too...

PD
PS Yeah, it was meant for displaying on the laptop screen, not printing. That is a lot of black!