COGMIND.
COGMIND COGMIND COGMIND.
Cogmind is legitimately the most underrated "real" roguelike around. Everyone knows about CDDA and Caves of Qud or whatever, I never see anyone talk about Cogmind. It's such a rabbit hole both gameplay and actually story-wise (because yeah, it actually has a story, despite being a traditional roguelike) that I can't help but wonder how the hell it's developer keeps going.
They have a blog where they talk about the game. It's borderline obsessive.
If I look at any one aspect of it closely I inevitably end up going "wait, what the hell?" because it goes farther than I expected. In-game computer terminals, the way word of your presence travels throughout the caverns you're in, each tile actually being a 3x3 space which affects how much "cover" you have... playing for quite a few hours before meeting other truly sentient robots and realizing that oh, there's, like, lore. A lot of it.