Illuminati - A loosely connected group of warring factions united by their common goal of staying in power ruling over all of us, aided by having each made alliances with various Vril in the far past leading to wealth and power that has lasted all the way to today. (Vril had access to precious minerals living underground and traded earthly riches with humans for secrecy and human victims).

References in Movies, TV, Music, etc - Incalculable

Related concepts - Basically everything

Notes - What you really need to understand is that the "Illuminati" is just an old vague name that kinda stuck, there are so many factions and sub factions all born from various events that resulted in power being attained, conquered, absorbed, dismantled, re-absorbed, re-structured, re-evaluated, re-conquered over so much time. The Illuminati is just the group of groups that collectively rule the world through evil means, forced to be part of this group out of necessity, a ring if you will of the most powerful people, one ring to rule them all..

Even though it might sound fancy its not, even they understand how kinda stupid their name sounds, its a Brand, a brand that most people wear, because they have to, you don't get beyond a certain point in this world without dealing with them, they like to think they are superior, enlightened, "Illuminated" but they know they aren't.
The most aware ones there know there is nothing mystical or magical about this system, they know its just the latest version of a long time tradition of allying with Vril for power translated into modern day with technology, it has all been said, it has all been done, they are the most powerful and have lived and seen so much, nothing is new, excepting the odd individual that excels.
There is much more to this structure than just humans and Vril but we shall go in that later.
For now just understand, these people Are Just people, yes they have influence but no they aren't superior.
Most of them nowadays had the bad luck of being born into it one way or another and know no other kind of existence.
This is why the story of the high echelon personality wanting to retreat to a lower class normal life is a trope.

Their lives are so different, so alien to how most of us have lived that it seems like another plane of existence.
The stress, the pain, the weight of living the kind of lives some people have been born into has turned many insane, this system engineers sociopaths who choose not to recognize the suffering in humanity as a means of coping out of necessity because if they don't go along with what happens they will be killed or worse.
The same goes for people who find themselves making a deal with the Illuminati which translates to prostituting yourself in basically every way imaginable and more for a life that on the surface seems perfect but comes at great personal cost which can never, ever be publicly discussed, this system embraces the worst aspects of people and encourages and feeds them to be even worse, as if its respectable.

The ultimate result of perpetuating evil and distilling it over time with technology and power.

Thats enough about that I think.