One of the best and most influential roguelikes ever made and my most played game of all time by a mile—was an active player for over a decade and still regularly make my way back when reaching for something familiar. Big focus on tactical combat and intelligent use of resources while still keeping a sense of mystery and discovery, especially while you’re still learning the game. DCSS is open source and still in active development too so nearly fifteen years after I first started playing it’s still getting active balance changes and content updates which is amazing. If you’re just getting started with traditional roguelikes DCSS is a great jumping off point, especially for free.