I think the Mind Flayer would be one of these two beings in mythology if I answered this question.
The Mind Flayer's Identity is unknown and so are it's origins but I think I have some good canadates.
1. Zahhāk
This guy would be my first answer since he has snakes as tenticles and has a head. This guy would also be a great canadate since he has an objective in conquering our world like the Mind Flayer.
His origin Story of being the King of Babylon and being slayed by a hero for his evil deeds could be a reason why he wants revenge on Earth.
He is described as a sorcerer who ruled with the aid of demons, the daevas (divs). These daevas could be controled by him as the Demogorgons are controled by the Mind Flayer and he ruled with them by his side as the Mind Flayer rules the Upside Down with Demogorgons by his side.
The Middle Persian sources also prophesy that at the end of the world, Dahāg will at last burst his bonds and ravage the world, consuming one in three humans and livestock. Kirsāsp, the ancient hero who had killed the Az ī Srūwar, returns to life to kill Dahāg. This reincarnation of Kirsāsp could be Will or Eleven, which would be why Will got kidnapped by a Demogorgon in Season 1 or why in Season 3 he targeted Eleven.
He also transformed into a Supernatrual monster that looked like this.
And that looks almost like the Mind Flayer here.
So thats why I think Zahhak the Snake King from Persian Mythology could possibly be the Mind Flayer.