If you're a fan of creature collecting and in-depth RPG mechanics, I've got a game for you: Siralim Ultimate, the latest release in the indie RPG series of monster collecting and combining games. It's all about building up a party of powerful monsters, combining the best into other, more powerful monsters, throwing them into 6v6 monster battles, and using them to clear not just a main story but bojillions of procedurally generated dungeons.
Siralim Ultimate is the fourth game in the series, with the previous three released over the last five years. It spent the last few months in Early Access, and as of writing has 95% positive reviews. Ultimate's got a lot going on, with more than 1200 creatures, each with its own unique ability, all of which can be combined into millions of permutations, and finally influenced by each of 30 different character classes. You can also do... a lot more.
There are artifacts to equip your creatures with, and spell gems, and honestly I believe the developers when they say that the sufficiently devoted could play this game forever. It is rare that I don't call bull-honkey on the phrase "Infinite End-Game Content" but I'm pretty sure you'll get tired of Siralim Ultimate before you run out of stuff to do.
Siralim Ultimate is $20 US on Steam, where it's 10% off until December 10th, 2021.