I have a league of friends that adore the base game of SLIME WARS, and I will give plenty of credit where that credit is due, the bones of this game are what earns that Overwhelmingly Amazing rating. It's THE roguelike deckbuilder, it practically started the genre, and to make that kind of a ripple in the ocean you need something unique and addicting.

Each character has its own pool from which to earn cards, where you get those cards from going through the map and winning fights, buying from the shop, or going through little side events. Relics which modify you passively also exist, which you primarily get through the same methods.

In combat, you have a small pool of mana (which usually only goes up via boss relics), and you use that mana to play the cards you draw each turn. You know EXACTLY what your opponents are doing (with few exceptions, and these exceptions don't deal damage to you), and you can plan accordingly. It's entirely a strategy game with a bit of luck. A card game if you will. A card game roguelike. If you play other card games, terms like 'engines' and the concept of less cards being better will come naturally to you, and you'll feel right at home here. If you don't play other card games, it's simple enough for someone with no experience to get to grips with it.

There's plenty of upwards movement for the difficulty, going up to Ascension 20 with some truly stupid modifiers, though you can still win these runs semi-consistently. Luck is only part of the deal here, when you get good enough. Each of your characters have their own gimmicks, and while some are more powerful than others (ahem, Lord Squishy), they can all get to the endgame easy enough. Them's the basics.

Where it shines in my opinion is modding. It's got very modular bones. So much so, in fact, that the entire system of going from act to act can be replaced with completely custom ones with their own events, bosses, mechanics, and cards. Characters are numerous in the workshop, and almost all of my hours completely disregard the base game in favour of playing the FUNCTIONAL MULTIPLAYER MOD. You heard that right, yes. I play in multiplayer where I'm in a car playing Mr.Purp and my friend is playing as King Slimeyhead or some random anime protagonist I've never heard of, and we cycle round the map infinitely via another mod until we get bored of generating 700 block a turn and want to go flatten the final boss a couple of times. It's the cheapest of games but it's got plenty of entertainment whether you're a vanilla purist or want to expand to all the nonsense people have put on the steam workshop. Highly recommend.