Who would like to follow me into some desolate ruins full of traps, murky shadows, and demonic cultists?
Nobody? C'mon, it'll be.... fun!
Jokes aside, it would actually be a horrifying experience, and if you even survived those dangers in the first place, escaping the very likely risk of bodily harm, your mind would most definitely be affected, even if it's just a little stress (or a lot). This is what Darkest Dungeon explores, and the mechanic that your party gets stressed on top of being turned to hamburger makes for very interesting games. Picture this: Your healer is working overtime, buffing and patching up everyone, but what you're not watching is her stress level. All of a sudden, a skeleton lands a critical hit on her, and she goes into mental overload and... has a nervous breakdown. Now, your healer can still heal, but will do so far less efficiently.
Darkest Dungeon plays out as a turn based tactical RPG where you control a party of four unfortunates on missions to clear up your mansion (congratulations, you're rich) of all the filth, demon pigs, bandits, and cultists that have invaded (Your new mansion kinda comes with all these). The objective of the game is (as far as I can tell) is to finish all the objectives (kill a bunch of named bosses, clear out dungeons, and upgrade the town around your mansion so it looks like a place where you won't get mugged on a daily basis. Your adventurers will shuffle in a sidescrolling manner from room to room, looting chests they find, killing enemies, contracting deadly diseases like "The Runs", and most importantly, keeping their torches lit. The game provides another interesting mechanic with this: the way is lit for as long as the torch is lit, providing nifty bonuses to your heroes, but once it wanes and dies.... things go south fast. Your party will get surprised often, get stressed more, and miss attacks as if they were drunk.
Now, all of this is very nice and all, but the most important thing I will say about this game is that you will hate it beyond any possible means a human has to hate it. And then you will play it again, and again and again. Just like XCOM, you have a base and a customizable squad and a sense of progression everytime you see your base grow.... but you'll also see your team members die. A lot. And guess what? They stay dead forever, just like in real life. There's even a little graveyard in your town to commemorate your fallen heroes. This means that you'll be under intense pressure whenever you choose who to take for your net mission... and how you act while you're on it. Do you choose your buffed up high level character with good armor and high skills... or do you keep him in the town roster where he's nice and safe since he could get whacked on the mission (and lose all that preparation and good armor and stuff)?
All in all, this game will infuriate you, make you gnash your teeth, and quite possibly result in you punching a hole in your monitor. But rest assured that all your righteous fury will come to a satisfying conclusion because let me tell you something: There is no greater pleasure in this world than finally smiting that uber-strong boss that wiped out an entire party, and returning victorious back to your town.