Pro Great monster design
There's a wide variety of extremely well-designed monsters and characters in the game. You confront bandits, skeletons, fish men, pig monsters, and all sorts of Eldritch horrors.
But what's really noteworthy though is the boss monsters design. Both the art style and abilities are unique and hard to find in other games. For example, there's a boss which is pretty much a lump of flesh that can transform into a Siren and even seduce one of your allies to its side temporarily.
Pro The gameplay constantly keeps you on the edge
The rampant and merciless randomness built into the gameplay always manages to keep the player on the edge. Even the turns in which characters are allowed to do their actions is decided randomly behind the scenes.
For example, you might be planning to heal one of your characters with your healer next turn, but you can never be quite sure whether you'll be able to or whether the enemy will deal the killing blow
Pro Has some outstanding narration that adds a lot to the great atmosphere and backstory of the game
The voice actor who does the narration is excellent. He portrays an ancestor of the player character who first discovered the dungeons you are exploring but then lost his mind from what he discovered in there. This tiny bit of backstory does a lot to add to the overall Lovecraftian feel of the game.
Before fighting a boss monster, the narrator will jump in to explain the backstory of that monster and the role it played in the maddening quest of the character's ancestor himself.