Interesting. I found something similar in a different part of the world. In those cultures, apparently they mean well (and not the malevolent image David Icke has painted of them). They are also not considered Gods, although still worshipped as they are half-divine. There are multiple levels of divinity below what would be considered "God" in a Christian sense.
naga, in Hinduism, Buddhism, and Jainism, a member of a class of mythical semidivine beings, half human and half cobra. They are a strong, handsome species who can assume either wholly human or wholly serpentine form and are potentially dangerous but often beneficial to humans.
The creator deity Brahma relegated the nagas to the nether regions when they became too populous on earth and commanded them to bite only the truly evil or those destined to die prematurely.
Note: I believe "nether regions" could be a mistranslation, and doesn't mean below the ground (or on Earth necessarily).
Brahma is one of the three top Gods, all three considered equal in some sects while in others one of the three (eg: Vishnu) is considered the original.
The female nagas (naginis or nagis) are serpent princesses of striking beauty. The dynasties of Manipur in northeastern India, the Pallavas in southern India, and the ruling family of Funan (ancient Indochina) each claimed an origin in the union of a human being and a nagi.
They aren't depicted with a tall skull though, only a serpentine lower body: https://fineartamerica.com/featured/nagas-at-rajarani-temple-orissa-india-david-wells.html
Unfortunately the Muslim invaders destroyed most temples in Northern India and also burned the largest library in the world at the time, even though it was a doctor from that university that saved his life (at Nalanda University which had 9 million manuscripts). So most of the Indian heritage is lost.
Although currently, the Church has also joined in trying to destroy the India that remains (India receives the most amount of aid, a lot of which is used to convert people). The demographic changes in some parts of India are astounding, and used for political purposes. It is basically a continuous stream of invasions on a civilizational level going on for the last 1000 years. You can understand why Indians hate Abrahamic faiths (except Jews, who haven't (openly) tried to subvert it).
I think the Tuatha de Danaan may have been nagas.
And they did move underground.
Now, there's underground and there's Hell.
They didn't go to Hell.
They went to live in underground worlds, cities. We know such cities exist.
If you've been to the DC area, then you know there are whole shopping centers underground -- one of them is Crystal City.
It's not a big thing. You get used to it.
Crystal City is an urban neighborhood in the southeastern corner of Arlington County, Virginia, south of downtown Washington, D.C. Due to its extensive integration of office buildings and residential high-rise buildings using underground corridors, travel between stores, offices, and residences is possible without going above ground; thus, a large part of Crystal City is an underground city.
Now, here is something interesting:
Crystal City includes offices of numerous defense contractors, the United States Department of Labor, the United States Marshals Service, and many satellite offices for The Pentagon. It is also the location of Ronald Reagan Washington National Airport.