I'd like to bring your attention to a really awesome rogue-like card battler game that's about as close as you can get to Slay the Spire while still having its very own identity and feel:
The free base game is standalone, complete and absolutely offers a ton of replayability. It's, I feel, incorrectly tagged as "Free to Play" in Steam, but it has no micro-transactions or anything. You get the full unlimited dungeon-run style game and the first two characters, Knight and Ranger, for free. It's entirely PVE and you can play it to your heart's content without ever paying anything.
It has a bunch of DLCs, most of which add another playable character and/or game mode and/or tons of extra cards, boss fights and so on, and they're all really good and dirt cheap, for the most part. The most "expensive" costs a bit above €3 and it adds so much it might as well be called "Night of the Full Moon 2". Otherwise, you can skip the €1.59 memory puzzle DLC, which barely adds anything to the main game (unless you're really really into basic puzzles), and the other 5 DLCs each cost only €0.79 and are really worth it. But you don't need any of them to enjoy the game for dozens of hours!
For some reason, it's never recommended to anyone even when actively searching for rogue-likes, card battlers or even specifically for games similar to Slay the Spire. It should be the number 1 recommendation for anyone who has ever played any roguelike on Steam, but it's actually pretty hard to find, and I stumbled upon it by pure chance. So I'd like to make sure you guys don't miss out.
ONE important thing to know is that if you don't have your Regional Format setting in Windows set to an English variant (any country), then it might cause visual bugs. You can change it in a couple of clicks from the Control Panel, though (and it doesn't affect your keyboard layout or much else):
Enjoy!