Ea R'lyeh Aboleths.

[HoneyBadger]

What do you think mechs and death rays and Darth Vader and C'thulhu/Lovecraft are, if not mythology? Besides, have you taken a close look at what's already in the game? We have mechanical men, we have hyper intelligent Pretender squid-gods with magical powers (Ancient Kraken), we have a king of the Fomorians that has a death ray for an eye...Everything you mentioned, aside from a Darth Vader clone, is already in there without ever touching on Lovecraft, and for more far-fetched reasons than alien (to humans) technology.

The game doesn't need to be completely humanocentric, and it doesn't need to be totally based on our best guess of whatever we imagine some culture's world-view might have been 1500 years ago. Neither of those things add anything to the game, they're just self-imposed limitations that frown on the idea that people today might have imaginations as important and valid as they did in ages past.

And really, discussing why you don't want Aboleths-a made up race probably invented by Gary Gygax in the 70's-to be somehow tainted by a more purple shade of weirdness than you're comfortable having applied to giant, sentient, mudfish/squids that are born from giant holy corals...I just don't know where to begin.