Eternal Darkness is a game for the GameCube and was the first Nintendo published game to receive a Mature rating by the ESRB. If you play the game today, I think most will agree that that rating was a bit too much. But the damage was already done, the game didn't sell enough copies and was a commercial failure. A decade later, two attempts by the game director to finance a successor via kickstarter failed, so it seems the game is as cursed as its protagonists.
But why do I recommend it here to you?
Because it has a great story and atmosphere (two big criteria for me in games) and it also has a fascinating (but sadly underused) magic system. The magic system is based on runes, which you can freely combine to try and cast a spell. You will also find translations of a rune and the recipes for spells, but in principle you could cast every spell if you have access to the runes and want to try things. The runes correspond to either a verb or a noun. If you combine Protect with Self, you will cast a shield on you. If you instead combine Protect with Area, you will place an enemy damaging area on the ground. Sadly they did not utilize this magic system to do many interesting things, as you can only combine one verb with one noun and that's it. You will find greater magic circles where you can put in more runes and in principle could cast more complex spells. But alas, they only allow you to put more Pargon runes, which just increase the power of the normal spell. Since every rune is voiced after you cast a spell, I think the last memory of my dying brain will be pargon, pargon, pargon...
The game is horror themed but doesn't include jump scares (with one exception), but instead tries to unnerve the player via sanity effects, as befits its name. Sanity is one of the resources next to health and mana and when it gets low, the chance increases that something will happen, maybe while changing the rooms you will enter an upside down room or your controls will be mirrored. They even included some meta fourth wall breaking stuff like decreasing sound. But nowadays those will not work on you any longer, as the interface looks different today. But still, the goal was to fuck with the players mind and that they achieved. You often question yourself while playing: is that real or not? Which is a masterfully done mechanic for a cosmic horror game.
And did I mention that they patented this and thereby hindered other developers from doing fun stuff like that? Maybe it was deserved karma that the game failed...
But now onto the story and atmosphere: in the game you don't fight against a cosmic horror, but instead three. They each keep one other in balance, so that no one can get the upper hand without being overpowered by the third one. But there are plans in motion to topple this delicate balance. And you are only able to interfere with these plans, because you are the pawn of anotger ancient one yourself. The binding element throughout the story is the Tome of Eternal Darkness, which binds the wearer to it in a nice little ritual with a floor of eternal damned souls and architecture made of bones, oh and did I mention the suspiciously agonized looking statues of the former hosts? Oh and did I mention that the book is bound in human leather and bones? Yeah, your patron isn't exactly nice either. Armed with this good book you fight and puzzle your way through different places around the world which you visit multiple times at different epochs from antiquity to our modern era.
This cosmic horror atmosphere of never really being totally in control is in my opinion wonderfully captured in this game. And due to time shenanigans, it is also made clear, that the power scale is so far outside of humans reach, that cosmic horror insanity is the only sane response.
The controls aren't exactly the strength of the game, but it is functional after getting used to them. If you want to play it nowadays, emulation is probably the easiest way to do that. I used that and was glad for the additional save states and higher resolution.