Nergal is a Mesopotamian God of the underworld. He’s known to be associated with mass destruction, plague, warfare and pestilence. He is a pre-Judaic Arabian God who was worshipped throughout Mesopotamia (Akkad, Assyria and Babylonia), and is the son of Enlil and Ninlil
This deity of the desert is connected to Bulls and Lions. He represents the sun of noontime and of the summer solstice, as the high summer is the dead season in the Mesopotamian cycle.
Nergal is mentioned in the Hebrew bible as the deity of the city of Cuth and there is evidence of his cult in Canaan and Athens. As a God of fire and death he is sometimes called a demon and has been identified with Satan
Nergal represents a particular aspect of death, as death brought on by him has a supernatural dimension. Disease often being attributed to demonic agency in Mesopotamia.
He controls a variety of demons and evil forces. The most notorious of these being the “seven gods” in the myth of Erra as agents of death and destruction.
Now, the story of how he became King of the Underworld is that he was thrown out of Heaven and he stormed the underworld with 14 demons. The Goddess Ereshkigal was queen and Nergal threatened to cut off her head. The only reason she survived was because Ereshkigal said she would be his wife.
The thing about Gods like Nergal is that they serve a purpose too. Not all Gods and Goddesses are good and loving. Although I have yet to meet anyone who actually worships a dark deity, one needs to be aware of them and still offer them respect.