zero_spelled_with_an_ecks

Western setting where a new gold rush for dark stone pits gunslingers, lawmen, saloon girls, etc against tentacles, the undead, mutated gangsters, snakemen, and lost technology as they travel between worlds.

It's coop and there are different missions, most of which have randomly generated maps that are created from a deck on you explore, giving it endless replayability. Characters gain experience, skill, and gear but also can become injured or mutate (nothing the church or surgeon in town can't fix for a price).

It also has tons of expansions. While the physical games add up in cost and require a lot of organizing, you can give it a try on tabletop simulator.

There's even a Japanese themed set that can combine with the Western ones.