I've never been much into card games on PC, unless you count poker—which is why when a fantasy card game has some poker in it I tend to pounce. I played We Slay Monsters last year, a turn-based RPG built around poker hands, but more recently I starting using The Poker Player mod for Slay the Spire.
The Poker Player mod adds a new character, who unfortunately doesn't have any custom art so it just looks like the Ironclad. But where the mod lacks art it makes up for with a fun twist on Slay the Spire. It adds 40 playing cards with suits (clubs, diamonds, aces, and hearts) and ranks (1-10). There are also a bunch of new specialty cards built around the poker systems, and new relics to enhance your play.
The general idea is that you're trying to build the best poker hand—pair, two pair, three of a kind, straight, flush, full house, four of a kind, straight flush. The fun thing about the mod is that your poker hand gets played at the end of your turn: the showdown. So rather than trying to do damage, add block, and use buffs during your turn, you mostly do it at the very end when your hand is put together. It's a fun twist on standard Slay the Spire, and takes some getting used to.
Your poker cards each cost one energy, and you can discard them in exchange for a new one from your draw pile until you're out of energy. (Or if you've put together a good hand you can end your turn early.) Each suit also does something specific: clubs deal damage to all enemies, diamonds do damage to the enemy with the lowest HP, spades give you block, and hearts (cleverly) heal your own HP. These effects are boosted by how good your poker hand is when you've reached the showdown at the end of your turn. So in addition to trying to build a good poker hand, you're trying to build a hand in the suit that benefits you most depending on your current monster situation.
It can get tricky at times. You can still find a few standard cards when adding to your deck, but they kind of get in the way of your poker hands since when you use them you wind up with fewer than five cards in the showdown. And when you're fighting enemies that add cards to your deck (like slimed or dazed) and your deck fills up with those extra cards, it can be hard putting together anything besides a pair or three of a kind. But that's the challenge, and it's fun. (You are protected from the first six status cards added to your deck thanks to the default poker relic, but six is never enough, is it?)
There are some nice zero-cost cards added by the mod that let you discard unwanted cards or peek at your draw pile to see what's next or add a few extra cards of a certain suit. And you can upgrade your poker cards just like you can standard cards—so if you're not making enough straights you can craft a six out of an extra five, and so on.
As you might guess there are number of vanilla cards, potions, and relics that the mod restricts you from using because they'd really muck things up (like Runic Pyramid, which lets you keep cards at the end of your turn, and the Swift potion, which lets you draw three cards). Even some events have been modified to fit the poker theme.
I do wish the art in the mod was better, but The Poker Player has been very well thought out and I'd recommend it to poker lovers and anyone who is looking for a new twist on Slay the Spire—it really lets you approach the game differently. You can subscribe to The Poker Player in the Steam Workshop here, and you'll also need these three base mods: Basemod, StsLib, and Mod The Spire.