You are all the Devil.
Old Nick. Lucifer. It doesn't really matter which name you adopt, he's inside every one of you. I'm sorry if you're of a somewhat religious persuasion and this news comes as a bit of a shock. Don't be alarmed. Try to shed the idea of the Devil being a manifestation of all evil. We're talking here about temptation, about free will. About rebellion.
It's a mistake to think that Satanic themes are only present in games that feature hellish or demonic imagery. Every game, after all, has a player. That player is you. And you are the Devil. Specifically, the Devil is a manifestation of your agency (capacity to act) as a player.
The game designer is essentially a Judeo-Christian style god. He is all-powerful and can tell the player precisely what can and cannot be done within his universe. Generally, he will know exactly how the plot unfolds and often attempts to steer the player down the "correct" narrative path, one that just happens to correspond with his design vision. Guidance arrows and pop-up control hints are his Ten Commandments. Obey these and you will take your place in heaven. You'll achieve enlightenment. You'll finish the game.
Even in cases where we are apparently given free will as players, this freedom is often an illusion. Open-world and sandbox games all have their limitations. Projects like Mount & Blade offer a tremendous amount of player freedom (especially compared to your average corridor shooter), but even these titles eventually fall prey to invisible design barrier syndrome. In Mount & Blade, I'm a heavily armored horse-riding fellow. So why can't I terrorize a village, picking off the inhabitants one by one, until the local Lord agrees to pay me a protection fee? Why can't I practice standing upright on the back of my horse and then travel around the land performing my one man horse-surfing act for the amazement of thousands of wide-eyed peasants?
Restrictions like these may be the result of engine limitations or simple oversights, but more often than not they are present because the activities were not part of the designer's grand plan. He works in mysterious ways.
As a result, John Milton's popularized portrayal of the Devil as a rebel in Paradise Lost is something that should resonate with all players. When the imposed rules of a game are too restrictive, we have a burning desire to break them. We want to clamber around where we're not supposed to go, to circumvent invisible barriers and to use what meager powers we have been given in unforeseen ways. Like Milton's charismatic version of Satan, we wish to challenge the creator's authority over us, even if these acts end in failure. Few things frustrate players more than arbitrary rules placed upon us by all-knowing games designers. After all, what use is the freedom to watch mighty powers being unleashed in a multitude of unskippable cut-scenes if the ability to progress in-game is still thwarted by a tiny fence?
Player agency, then, is a manifestation of our desire to rebel against a creator. It's the serpent in the Garden of Eden, whispering to us that the designer is keeping something from us and that if we only act against his wishes, these new paths will be revealed to us. God may have given Adam and Eve free will in the Book of Genesis, but it was the Devil who encouraged them to truly exercise it. We should all take a bite from that apple - unless prompted to do so by "Press A to eat." In that instance, we should instead try to escape over the walls of the garden by stacking all of the animals in a big tower.