The first thing you need to know about The Eternal Castle is it's a remaster of the 1987 original of the same name. Well... except it isn't. This ruse could easily be a gag or pretentious bullshit but the pretence it's a remaster of a game that came out decades ago is the first clue this game is about the past.
Set in the far flung future, The Eternal Castle has a deliberately vague plot but the key details aren't hard to unravel. An attempt to flee earth to other worlds ended with a load of colonists stuck in stasis on a ship in the Earth's orbit, all while the planet below fell into chaos. Playing as one of these colonists, Adam or Eve, your choice, your ship crashes on Earth. From there it's a romp through a mish mash of pulpy post-apocalyptic and science fiction vignettes; the mad scientist's lair, a set of war-torn ruins and an overgrown temple ruled by a cult.
The first thing anyone is going to notice is the visuals. This blown out 2-bit world is striking as all hell, entire landscapes stripped down to silhouettes and ghosts. While to play it will be familiar to anyone who's touched any modern cinematic platformer like Inside or Little Nightmares, its visuals make it clear it has roots in much older games like Another World and Flashback.